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question:Given the function f(x, z) = 2x^2 + y - z, and f(2, 3) = 100, find the value of f(5, 7).
answer:First, I need to determine the value of ( y ) using the given information ( f(2, 3) = 100 ).Given the function ( f(x, z) = 2x^2 + y - z ), substitute ( x = 2 ) and ( z = 3 ):[f(2, 3) = 2(2)^2 + y - 3 = 100]Simplify the equation:[8 + y - 3 = 100]Combine like terms:[y + 5 = 100]Solve for ( y ):[y = 95]Now, with ( y = 95 ), calculate ( f(5, 7) ):[f(5, 7) = 2(5)^2 + 95 - 7]Simplify the equation:[50 + 95 - 7 = 138]Therefore, the value of ( f(5, 7) ) is 138.
question:Compute the expression: 4sin 60^{circ}-|-2|-sqrt {12}+(-1)^{2016}.
answer:First, I need to compute each part of the expression separately.1. **Compute (4sin 60^{circ}):** - I know that (sin 60^{circ} = frac{sqrt{3}}{2}). - Multiplying by 4 gives (4 times frac{sqrt{3}}{2} = 2sqrt{3}).2. **Compute (|-2|):** - The absolute value of (-2) is (2).3. **Compute (sqrt{12}):** - I can simplify (sqrt{12}) by factoring it into (sqrt{4 times 3}). - This simplifies to (2sqrt{3}).4. **Compute ((-1)^{2016}):** - Since the exponent is even, ((-1)^{2016} = 1).Now, I substitute these computed values back into the original expression:[4sin 60^{circ} - |-2| - sqrt{12} + (-1)^{2016} = 2sqrt{3} - 2 - 2sqrt{3} + 1]Next, I simplify the expression by combining like terms:[2sqrt{3} - 2 - 2sqrt{3} + 1 = (2sqrt{3} - 2sqrt{3}) + (-2 + 1) = 0 - 1 = -1]Therefore, the final result of the expression is (-1).
question:Let the function f(x) = |2x+2| - |x-2|.- (1) Find the solution set of the inequality f(x) > 2;- (2) Given x in mathbb{R}, f(x) < 2 - frac{7}{2} t has a solution, find the range of the real number t.
answer:Okay, so I have this function f(x) = |2x + 2| - |x - 2|, and I need to solve two problems related to it. Let me take them one at a time.Starting with part (1): Find the solution set of the inequality f(x) > 2.Hmm, since the function involves absolute values, I remember that I need to consider different cases based on the critical points where the expressions inside the absolute values change their signs. For |2x + 2|, the critical point is when 2x + 2 = 0, which is x = -1. For |x - 2|, the critical point is when x - 2 = 0, which is x = 2. So, I should break down the function into intervals based on these critical points: x < -1, -1 ≤ x < 2, and x ≥ 2.Let me write down the function f(x) in each interval.1. When x < -1: - 2x + 2 is negative because 2x < -2, so |2x + 2| = -(2x + 2) = -2x - 2. - x - 2 is also negative because x < -1 < 2, so |x - 2| = -(x - 2) = -x + 2. - Therefore, f(x) = (-2x - 2) - (-x + 2) = -2x - 2 + x - 2 = (-2x + x) + (-2 - 2) = -x - 4.2. When -1 ≤ x < 2: - 2x + 2 is non-negative because 2x ≥ -2, so |2x + 2| = 2x + 2. - x - 2 is still negative because x < 2, so |x - 2| = -x + 2. - Therefore, f(x) = (2x + 2) - (-x + 2) = 2x + 2 + x - 2 = 3x.3. When x ≥ 2: - 2x + 2 is positive because x ≥ 2, so |2x + 2| = 2x + 2. - x - 2 is non-negative because x ≥ 2, so |x - 2| = x - 2. - Therefore, f(x) = (2x + 2) - (x - 2) = 2x + 2 - x + 2 = x + 4.Okay, so now I have f(x) expressed as a piecewise function:f(x) = { -x - 4, if x < -1 3x, if -1 ≤ x < 2 x + 4, if x ≥ 2}Now, I need to solve f(x) > 2 in each interval.Starting with the first interval: x < -1.f(x) = -x - 4 > 2So, -x - 4 > 2Adding 4 to both sides: -x > 6Multiplying both sides by -1 (remember to reverse the inequality): x < -6So, in this interval, the solution is x < -6.Next, the second interval: -1 ≤ x < 2.f(x) = 3x > 2Divide both sides by 3: x > 2/3But since this interval is from -1 to 2, the solution here is 2/3 < x < 2.Third interval: x ≥ 2.f(x) = x + 4 > 2Subtract 4 from both sides: x > -2But in this interval, x is already ≥ 2, which is certainly greater than -2. So, the entire interval x ≥ 2 satisfies the inequality.Putting it all together, the solution set is x < -6 or x > 2/3.Wait, hold on. Let me double-check. In the first interval, x < -1, so x < -6 is a subset of that. In the second interval, x between -1 and 2, so x > 2/3 in that range is 2/3 < x < 2. And in the third interval, x ≥ 2, which is all included. So, combining these, the solution is x < -6 or x > 2/3.Wait, but 2/3 is approximately 0.666, so x > 2/3 includes x from 2/3 to 2 and beyond. So, yes, that seems correct.So, for part (1), the solution set is all real numbers x such that x < -6 or x > 2/3.Moving on to part (2): Given x ∈ ℝ, f(x) < 2 - (7/2)t has a solution. Find the range of the real number t.Hmm, so we need to find all t such that there exists some x where f(x) < 2 - (7/2)t.In other words, the inequality f(x) < 2 - (7/2)t must have at least one solution x.This means that 2 - (7/2)t must be greater than the minimum value of f(x). Because if 2 - (7/2)t is greater than the minimum of f(x), then there exists some x where f(x) is less than that value.So, first, I need to find the minimum value of f(x).Looking back at the piecewise function:f(x) = { -x - 4, if x < -1 3x, if -1 ≤ x < 2 x + 4, if x ≥ 2}Let me analyze each piece.1. For x < -1: f(x) = -x - 4. As x approaches -1 from the left, f(x) approaches -(-1) - 4 = 1 - 4 = -3. As x becomes more negative, f(x) increases because -x becomes larger. So, the minimum in this interval is as x approaches -1, which is -3.2. For -1 ≤ x < 2: f(x) = 3x. At x = -1, f(-1) = 3*(-1) = -3. At x approaching 2, f(x) approaches 6. So, this is a linear function increasing from -3 to 6.3. For x ≥ 2: f(x) = x + 4. At x = 2, f(2) = 6. As x increases, f(x) increases without bound.So, the minimum value of f(x) is -3, occurring at x = -1.Therefore, for the inequality f(x) < 2 - (7/2)t to have a solution, we need 2 - (7/2)t > -3.Let me write that down:2 - (7/2)t > -3Now, solve for t.Subtract 2 from both sides:- (7/2)t > -5Multiply both sides by (-2/7). Remember, multiplying by a negative number reverses the inequality.t < (-5)*(-2/7) = 10/7 ≈ 1.42857Wait, hold on, let me do that step again.Wait, after subtracting 2:- (7/2)t > -5Multiply both sides by (-2/7):t < (-5)*(-2/7) = 10/7Wait, 10/7 is approximately 1.42857, but let me check if that's correct.Wait, 2 - (7/2)t > -3Subtract 2: - (7/2)t > -5Multiply both sides by (-2/7), flipping inequality: t < (10)/7Wait, 10/7 is approximately 1.42857, but 10/7 is about 1.42857, which is less than 2.But wait, let me think again. Is that the only condition?Wait, actually, f(x) can take values from -3 to infinity. So, to have f(x) < 2 - (7/2)t, we need 2 - (7/2)t to be greater than the minimum of f(x), which is -3.But wait, actually, if 2 - (7/2)t is greater than -3, then there exists some x where f(x) is less than that value because f(x) can go down to -3.But is that the only condition? Or is there another condition?Wait, actually, if 2 - (7/2)t is greater than the minimum, then yes, the inequality f(x) < 2 - (7/2)t will have solutions because f(x) can be as low as -3.But wait, actually, f(x) can be greater than or equal to -3, so if 2 - (7/2)t is greater than -3, then there exists x such that f(x) < 2 - (7/2)t.But wait, actually, if 2 - (7/2)t is greater than the minimum, then yes, it's possible.Wait, but let me think differently. Maybe I should consider the range of f(x). Since f(x) can be as low as -3 and goes to infinity, the inequality f(x) < C will have solutions as long as C is greater than -3.So, in this case, C is 2 - (7/2)t. So, 2 - (7/2)t must be greater than -3.So, 2 - (7/2)t > -3Solving:2 + 3 > (7/2)t5 > (7/2)tMultiply both sides by 2:10 > 7tDivide both sides by 7:10/7 > tSo, t < 10/7 ≈ 1.42857Wait, but 10/7 is approximately 1.42857, which is about 1.42857.But wait, the initial solution I had was t < 3/2 or t > 2, but that was incorrect.Wait, no, actually, in the initial solution, the user had a different approach, but I think I need to correct that.Wait, let me go back.Wait, in the initial problem statement, part (2) says: Given x ∈ ℝ, f(x) < 2 - (7/2)t has a solution, find the range of t.So, the inequality f(x) < 2 - (7/2)t must have at least one solution. So, the right-hand side must be greater than the minimum value of f(x), which is -3.So, 2 - (7/2)t > -3Solving:2 + 3 > (7/2)t5 > (7/2)tMultiply both sides by 2:10 > 7tDivide by 7:10/7 > tSo, t < 10/7 ≈ 1.42857But wait, 10/7 is approximately 1.42857, but in the initial solution, the user had t < 3/2 or t > 2, which is different.Wait, perhaps I made a mistake in interpreting the problem.Wait, let me check the original problem again.It says: Given x ∈ ℝ, f(x) < 2 - (7/2)t has a solution, find the range of the real number t.So, the inequality f(x) < 2 - (7/2)t must have at least one real solution x.So, the right-hand side must be greater than the minimum value of f(x), which is -3.So, 2 - (7/2)t > -3Which gives t < 10/7.But wait, 10/7 is approximately 1.42857, which is less than 3/2 (1.5). So, perhaps the initial solution was incorrect.Wait, but let me think again. Maybe I need to consider the maximum value as well?Wait, no, because f(x) can go to infinity, so for any C, if C is greater than the minimum, there will be x such that f(x) < C.Wait, but actually, if C is greater than the minimum, then yes, because f(x) can be as low as -3, so if C is greater than -3, then there exists x such that f(x) < C.Therefore, the condition is 2 - (7/2)t > -3, which simplifies to t < 10/7.But 10/7 is approximately 1.42857, which is less than 3/2 (1.5). So, the range of t is t < 10/7.But wait, in the initial solution, the user had t < 3/2 or t > 2, which is different.Wait, perhaps I made a mistake in the initial steps.Wait, let me re-examine the initial solution.In the initial solution, the user wrote:"From the above, we can see that the minimum value of f(x) is f(-1) = -3.If for all x ∈ ℝ, f(x) < t² - (7/2)t has a solution, then -3 < t² - (7/2)t must hold, which is equivalent to 2t² - 7t + 6 > 0. Solving this gives t < 3/2 or t > 2."Wait, but in the problem statement, it's f(x) < 2 - (7/2)t, not f(x) < t² - (7/2)t.So, the initial solution had a typo or mistake in the problem statement.Wait, in the problem statement, part (2) says: f(x) < 2 - (7/2)t.But in the initial solution, the user wrote f(x) < t² - (7/2)t.So, that was incorrect.Therefore, my approach is correct: the inequality is f(x) < 2 - (7/2)t, so we need 2 - (7/2)t > -3, leading to t < 10/7.But wait, let me double-check the algebra.Starting with 2 - (7/2)t > -3Subtract 2: - (7/2)t > -5Multiply both sides by (-2/7), flipping inequality: t < (10)/7Yes, that's correct.So, the range of t is t < 10/7.But 10/7 is approximately 1.42857, which is 1 and 3/7.But in the initial solution, the user had t < 3/2 or t > 2, which is different.Wait, perhaps the problem was miswritten.Wait, let me check the original problem again.The user wrote:"Given x ∈ ℝ, f(x) < 2 - (7/2) t has a solution, find the range of the real number t."So, it's 2 - (7/2)t.Therefore, the correct condition is 2 - (7/2)t > -3, leading to t < 10/7.But 10/7 is approximately 1.42857, which is less than 3/2 (1.5).Wait, but 10/7 is about 1.42857, which is less than 3/2 (1.5). So, the range is t < 10/7.But wait, let me think again. Is there any other condition?Wait, f(x) can be as large as possible, so if 2 - (7/2)t is greater than the minimum, then there exists x such that f(x) < 2 - (7/2)t.But if 2 - (7/2)t is less than or equal to the minimum, then no solution exists.Therefore, the condition is 2 - (7/2)t > -3, leading to t < 10/7.Therefore, the range of t is t < 10/7.But 10/7 is approximately 1.42857, which is less than 3/2 (1.5). So, the range is t < 10/7.Wait, but in the initial solution, the user had t < 3/2 or t > 2, which is different.Wait, perhaps the user made a mistake in the problem statement.Wait, in the initial problem statement, part (2) says: f(x) < 2 - (7/2)t has a solution.But in the initial solution, the user wrote f(x) < t² - (7/2)t.So, that was incorrect.Therefore, the correct condition is t < 10/7.But let me check again.Wait, 2 - (7/2)t > -3So, 2 + 3 > (7/2)t5 > (7/2)tMultiply both sides by 2: 10 > 7tSo, t < 10/7.Yes, that's correct.Therefore, the range of t is t < 10/7.But 10/7 is approximately 1.42857.Wait, but 10/7 is 1 and 3/7, which is about 1.42857.So, the range is t < 10/7.Therefore, the answer is t < 10/7.But in the initial solution, the user had t < 3/2 or t > 2, which is incorrect because they probably misread the problem as f(x) < t² - (7/2)t instead of f(x) < 2 - (7/2)t.Therefore, the correct answer is t < 10/7.But wait, let me think again. Is there any other condition?Wait, f(x) can be as large as possible, so if 2 - (7/2)t is greater than the minimum, then there exists x such that f(x) < 2 - (7/2)t.But if 2 - (7/2)t is less than or equal to the minimum, then no solution exists.Therefore, the condition is 2 - (7/2)t > -3, leading to t < 10/7.Therefore, the range of t is t < 10/7.So, the final answer is t < 10/7.But wait, 10/7 is approximately 1.42857, which is less than 3/2 (1.5). So, the range is t < 10/7.Therefore, the range of t is t < 10/7.Wait, but in the initial solution, the user had t < 3/2 or t > 2, which is different.So, perhaps the user made a mistake in the problem statement or in their solution.Therefore, the correct answer is t < 10/7.But let me write it as a fraction: 10/7.So, t < 10/7.Therefore, the range of t is all real numbers less than 10/7.So, in boxed form, it's boxed{t < dfrac{10}{7}}.But wait, in the initial solution, the user had t < 3/2 or t > 2, which is incorrect.Therefore, the correct answer is t < 10/7.
question:If x is real and positive and grows beyond all bounds, then log_3{(6x-5)}-log_3{(2x+1)} approaches:textbf{(A)} 0qquad textbf{(B)} 1qquad textbf{(C)} 3qquad textbf{(D)} 4qquad textbf{(E)} text{no finite number}
answer:Okay, so I have this problem here: If ( x ) is real and positive and grows beyond all bounds, then ( log_3{(6x-5)} - log_3{(2x+1)} ) approaches which of the options given? The options are 0, 1, 3, 4, or no finite number. Hmm, let me try to figure this out step by step.First, I remember that when you have the difference of two logarithms with the same base, you can combine them into a single logarithm using the quotient rule. The rule is ( log_b{A} - log_b{B} = log_b{left(frac{A}{B}right)} ). So applying that here, I can rewrite the expression as:[log_3{left(frac{6x - 5}{2x + 1}right)}]Alright, so now I have a single logarithm. The next step is to analyze what happens to the fraction inside the logarithm as ( x ) grows very large. When ( x ) is very large, the constants in the numerator and denominator become negligible compared to the terms with ( x ). So, I can approximate the fraction:[frac{6x - 5}{2x + 1} approx frac{6x}{2x} = 3]Wait, so as ( x ) becomes very large, the fraction approaches 3. That means the argument of the logarithm is approaching 3. Therefore, the expression becomes:[log_3{3}]And since ( log_3{3} = 1 ), because any logarithm of a number with its own base is 1, the entire expression approaches 1.But let me double-check to make sure I didn't skip any steps or make any mistakes. So, starting again, the original expression is ( log_3{(6x - 5)} - log_3{(2x + 1)} ). Using the logarithm quotient rule, it's ( log_3{left(frac{6x - 5}{2x + 1}right)} ). As ( x ) grows, the dominant terms are ( 6x ) in the numerator and ( 2x ) in the denominator, so the fraction simplifies to ( frac{6x}{2x} = 3 ). Therefore, the logarithm of 3 with base 3 is indeed 1.I think that makes sense. Another way to think about it is to divide both the numerator and the denominator by ( x ) to see the behavior as ( x ) approaches infinity:[frac{6x - 5}{2x + 1} = frac{6 - frac{5}{x}}{2 + frac{1}{x}}]As ( x ) approaches infinity, ( frac{5}{x} ) and ( frac{1}{x} ) both approach 0, so the fraction simplifies to ( frac{6}{2} = 3 ). So, again, the argument of the logarithm approaches 3, and ( log_3{3} = 1 ).Is there any chance that the answer could be something else? Let me consider if the expression inside the logarithm could approach a different value. If I didn't approximate and kept the constants, would it make a difference? Let's see:[frac{6x - 5}{2x + 1} = frac{6x - 5}{2x + 1}]If I factor out ( x ) from numerator and denominator:[frac{x(6 - frac{5}{x})}{x(2 + frac{1}{x})} = frac{6 - frac{5}{x}}{2 + frac{1}{x}}]As ( x ) approaches infinity, ( frac{5}{x} ) and ( frac{1}{x} ) both go to 0, so again, it's ( frac{6}{2} = 3 ). So, no, the constants don't affect the limit because they become insignificant compared to the terms with ( x ).Therefore, I'm confident that the expression inside the logarithm approaches 3, and the logarithm of 3 with base 3 is 1. So, the limit is 1.Wait, just to make sure, let me plug in a very large value of ( x ) and see numerically what happens. Let's say ( x = 10^6 ). Then:Numerator: ( 6x - 5 = 6,000,000 - 5 = 5,999,995 )Denominator: ( 2x + 1 = 2,000,000 + 1 = 2,000,001 )So, the fraction is ( frac{5,999,995}{2,000,001} approx 2.9999975 ), which is very close to 3. Then, ( log_3{2.9999975} ) is very close to 1. So, numerically, it also checks out.Another test with ( x = 10^9 ):Numerator: ( 6x - 5 = 6,000,000,000 - 5 = 5,999,999,995 )Denominator: ( 2x + 1 = 2,000,000,000 + 1 = 2,000,000,001 )Fraction: ( frac{5,999,999,995}{2,000,000,001} approx 2.9999999975 ), which is almost 3. So, ( log_3{2.9999999975} ) is practically 1.Therefore, all these methods confirm that the limit is 1. I don't think it approaches 0, 3, or 4, and it definitely approaches a finite number, so the answer must be 1.**Final Answer**boxed{B}
question:Given the function f(x)=|x+2|-2|x-1|.(1) Solve the inequality f(x)geqslant -2;(2) For any xin R, f(x)leqslant x-a always holds true. Find the range of values for the real number a.
answer:Okay, so I have this function f(x) = |x + 2| - 2|x - 1|. There are two parts to the problem. First, I need to solve the inequality f(x) ≥ -2. Second, I need to find the range of values for the real number a such that for any x in R, f(x) ≤ x - a always holds true.Let me start with the first part. I remember that when dealing with absolute value functions, it's helpful to break them down into different cases based on the critical points where the expressions inside the absolute values change their signs. For f(x) = |x + 2| - 2|x - 1|, the critical points occur where x + 2 = 0 and x - 1 = 0, which are x = -2 and x = 1, respectively. So, I'll divide the real number line into three intervals: x ≤ -2, -2 < x < 1, and x ≥ 1. In each interval, I can rewrite the function without the absolute value signs by considering the sign of each expression.Starting with x ≤ -2:In this interval, x + 2 is negative or zero, so |x + 2| = -(x + 2) = -x - 2.Similarly, x - 1 is also negative or zero, so |x - 1| = -(x - 1) = -x + 1.Therefore, f(x) = (-x - 2) - 2*(-x + 1) = -x - 2 + 2x - 2 = x - 4.Next, for -2 < x < 1:Here, x + 2 is positive, so |x + 2| = x + 2.But x - 1 is still negative, so |x - 1| = -(x - 1) = -x + 1.Thus, f(x) = (x + 2) - 2*(-x + 1) = x + 2 + 2x - 2 = 3x.Finally, for x ≥ 1:Both x + 2 and x - 1 are positive, so |x + 2| = x + 2 and |x - 1| = x - 1.Therefore, f(x) = (x + 2) - 2*(x - 1) = x + 2 - 2x + 2 = -x + 4.So, summarizing:- For x ≤ -2: f(x) = x - 4- For -2 < x < 1: f(x) = 3x- For x ≥ 1: f(x) = -x + 4Now, I need to solve f(x) ≥ -2 in each interval.Starting with x ≤ -2:f(x) = x - 4 ≥ -2So, x - 4 ≥ -2Adding 4 to both sides: x ≥ 2But wait, in this interval, x ≤ -2. So, x must satisfy both x ≥ 2 and x ≤ -2. But there's no overlap here because 2 is greater than -2. So, in this interval, there are no solutions.Moving on to -2 < x < 1:f(x) = 3x ≥ -2So, 3x ≥ -2Dividing both sides by 3: x ≥ -2/3But in this interval, x is between -2 and 1. So, the solutions here are x ≥ -2/3 and x < 1. So, the solution in this interval is -2/3 ≤ x < 1.Next, for x ≥ 1:f(x) = -x + 4 ≥ -2So, -x + 4 ≥ -2Subtracting 4 from both sides: -x ≥ -6Multiplying both sides by -1 (and reversing the inequality): x ≤ 6But in this interval, x is ≥ 1. So, the solutions here are 1 ≤ x ≤ 6.Combining the solutions from all intervals:From -2 < x < 1: -2/3 ≤ x < 1From x ≥ 1: 1 ≤ x ≤ 6So, overall, the solution set is -2/3 ≤ x ≤ 6.Wait, let me double-check. For x ≤ -2, there were no solutions. For -2 < x < 1, the solutions start at -2/3. For x ≥ 1, solutions go up to 6. So, combining these, the entire solution set is from -2/3 to 6. That seems correct.Now, moving on to the second part: For any x ∈ R, f(x) ≤ x - a always holds true. Find the range of values for the real number a.So, f(x) ≤ x - a for all x. That means, for every x, f(x) - x ≤ -a. So, if I define g(x) = f(x) - x, then g(x) ≤ -a for all x. Therefore, the maximum value of g(x) must be ≤ -a. Hence, a must be ≤ - (maximum of g(x)).So, I need to find the maximum value of g(x) = f(x) - x.Given that f(x) is piecewise defined, let's compute g(x) in each interval.First, for x ≤ -2:f(x) = x - 4So, g(x) = (x - 4) - x = -4For -2 < x < 1:f(x) = 3xSo, g(x) = 3x - x = 2xFor x ≥ 1:f(x) = -x + 4So, g(x) = (-x + 4) - x = -2x + 4So, g(x) is:- For x ≤ -2: g(x) = -4- For -2 < x < 1: g(x) = 2x- For x ≥ 1: g(x) = -2x + 4Now, let's analyze g(x) in each interval.For x ≤ -2: g(x) is constant at -4.For -2 < x < 1: g(x) = 2x. Since x is increasing from -2 to 1, g(x) increases from 2*(-2) = -4 to 2*(1) = 2. So, in this interval, g(x) ranges from -4 to 2.For x ≥ 1: g(x) = -2x + 4. As x increases, g(x) decreases. At x = 1, g(1) = -2*1 + 4 = 2. As x approaches infinity, g(x) approaches negative infinity.So, putting it all together, the maximum value of g(x) occurs at x = 1, where g(1) = 2. Therefore, the maximum of g(x) is 2.Thus, for g(x) ≤ -a to hold for all x, we must have 2 ≤ -a, which implies a ≤ -2.Wait, let me verify. If the maximum of g(x) is 2, then 2 ≤ -a, so a ≤ -2. That seems correct.But let me check for each interval:For x ≤ -2: g(x) = -4 ≤ -a. So, -4 ≤ -a ⇒ a ≤ 4.For -2 < x < 1: g(x) = 2x ≤ -a. The maximum of g(x) here is 2, so 2 ≤ -a ⇒ a ≤ -2.For x ≥ 1: g(x) = -2x + 4 ≤ -a. The maximum here is 2, so again 2 ≤ -a ⇒ a ≤ -2.Therefore, the most restrictive condition is a ≤ -2. So, the range of a is all real numbers less than or equal to -2.I think that makes sense. So, to recap:1. The solution to f(x) ≥ -2 is x between -2/3 and 6.2. The range of a is a ≤ -2.**Final Answer**(1) The solution set is boxed{left[ -dfrac{2}{3}, 6 right]}.(2) The range of values for ( a ) is boxed{(-infty, -2]}.
question:Participants in a spring math camp decided to give each other squares if they are acquaintances and circles if they are friends on Pi Day (March 14). Andrei found out that each boy received 3 circles and 8 squares, while each girl received 2 squares and 9 circles. Katya counted a total of 4046 figures given. Prove that one of them made a mistake.
answer:Okay, so I have this problem about participants in a spring math camp exchanging squares and circles based on whether they're acquaintances or friends. Andrei found out that each boy received 3 circles and 8 squares, while each girl received 2 squares and 9 circles. Katya counted a total of 4046 figures given. I need to prove that one of them made a mistake.Alright, let's break this down. First, let's understand what each participant receives. Boys get 3 circles and 8 squares, so that's a total of 3 + 8 = 11 figures per boy. Girls get 9 circles and 2 squares, so that's 9 + 2 = 11 figures per girl as well. Wait, both boys and girls receive 11 figures each? That seems interesting.But hold on, the problem says that squares are given if they are acquaintances and circles if they are friends. So, does that mean that the number of squares and circles each person receives depends on the number of acquaintances and friends they have? Hmm, maybe I need to consider the total number of squares and circles given by all participants.Let me denote the number of boys as ( b ) and the number of girls as ( g ). Each boy receives 3 circles and 8 squares, so the total number of circles received by all boys is ( 3b ) and the total number of squares is ( 8b ). Similarly, each girl receives 9 circles and 2 squares, so the total number of circles received by all girls is ( 9g ) and the total number of squares is ( 2g ).Now, the total number of circles given is ( 3b + 9g ) and the total number of squares given is ( 8b + 2g ). The total number of figures given is the sum of circles and squares, which is ( (3b + 9g) + (8b + 2g) = 11b + 11g ). Wait, that simplifies to ( 11(b + g) ).But Katya counted a total of 4046 figures. So, according to this, ( 11(b + g) = 4046 ). Let me check if 4046 is divisible by 11. Dividing 4046 by 11: 11 times 367 is 4037, and 4046 minus 4037 is 9. So, 4046 divided by 11 is 367 with a remainder of 9. That means 4046 is not divisible by 11, which is a problem because ( 11(b + g) ) must be divisible by 11.This suggests that there's a contradiction because the total number of figures should be a multiple of 11, but Katya counted 4046, which isn't a multiple of 11. Therefore, one of them must have made a mistake.Wait, let me make sure I didn't make a mistake in my calculations. So, each boy gets 3 circles and 8 squares, which is 11 figures. Each girl gets 9 circles and 2 squares, which is also 11 figures. So, regardless of the number of boys and girls, the total number of figures should always be a multiple of 11. Since 4046 isn't a multiple of 11, that means either the counts of figures per boy and girl are incorrect, or the total count of 4046 is wrong.Therefore, either Andrei made a mistake in reporting the number of circles and squares each boy and girl received, or Katya made a mistake in counting the total number of figures. Either way, one of them must have made a mistake.I think that's the reasoning. The key point is that the total number of figures must be a multiple of 11, but 4046 isn't, so there's an inconsistency.