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JAMB UTME - Mathematics - 2003

Question 1 Report

Determine the maximum value of y = 3x2 - x3
Answer Details
To find the maximum value of y = 3x^2 - x^3, we can take the derivative of y with respect to x, set it equal to zero, and solve for x. First, we find the derivative of y: dy/dx = 6x - 3x^2 Setting this equal to zero gives: 6x - 3x^2 = 0 Factor out x: x(6 - 3x) = 0 Solving for x, we get two solutions: x = 0 or x = 2 To determine which value of x gives the maximum value of y, we can use the second derivative test. Taking the second derivative of y: d^2y/dx^2 = 6 - 6x Plugging in x = 0 and x = 2: d^2y/dx^2 |x=0 = 6 > 0 d^2y/dx^2 |x=2 = -6 < 0 Since the second derivative is positive at x = 0 and negative at x = 2, this means that x = 0 corresponds to a minimum value of y, while x = 2 corresponds to a maximum value of y. Therefore, the maximum value of y = 3x^2 - x^3 occurs when x = 2, and is equal to: y = 3(2)^2 - (2)^3 = 4. So the answer is 4.