A curve has equation y = x^3 - 3x^2 -24x + 5, find the x co-ordinates of the two stationary points of the curve and hence determine whether they are maximum or minimum points.

y = x3 - 3x2 - 24x + 5, First, calculate the derivative of y and find its roots when y = 0:dy/dx = 3x2 - 6x -24 = 0 -> x2 - 2x - 8 = 0 -> (x+2)(x-4) = 0Therefore the coordinates of the stationary points are x = -2, 4. Now calculate the second derivative of y and insert these x values:d2y/dx2 = 6x - 6,For x = -2: d2y/dx2 = -12 - 8 = -18, this result is < 0 so this point is a maximum point.For x = 4, d2y/dx2 = 24 - 6 = 18, this result is > 0 so this point is a minimum point.

TS

Related Maths A Level answers

All answers ▸

How do you integrate (sinx)^2?


If cos(x)= 1/3 and x is acute, then find tan(x).


Find the x values for stationary points in the curve y=3sin(2x) for 0<x<180


A curve has equation y = 6ln(x) + x^2 -8x + 3. Find the exact values of the stationary points.