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Multiple Choice
Given the function , on which interval is the function increasing?
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Verified step by step guidance
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Step 1: To determine where the function f(x) = x^3 - 12x is increasing, calculate its derivative f'(x). The derivative represents the slope of the tangent line to the curve, and the function is increasing where f'(x) > 0.
Step 2: Compute the derivative of f(x). Using the power rule, f'(x) = 3x^2 - 12.
Step 3: Solve the inequality f'(x) > 0 to find the intervals where the function is increasing. Start by setting f'(x) = 0 to find the critical points: 3x^2 - 12 = 0. Solve for x to get x = ±2.
Step 4: Use the critical points x = -2 and x = 2 to divide the real number line into intervals: (-∞, -2), (-2, 2), and (2, ∞). Test the sign of f'(x) in each interval by choosing a test point within each interval and substituting it into f'(x).
Step 5: Based on the sign of f'(x) in each interval, determine where f'(x) > 0. The function f(x) is increasing on the intervals where f'(x) > 0. Combine these intervals to find the final answer.