Inactive Tutor answered 04/12/22
Take the derivative, set it equal to zero, and solve. Also, look for any place the derivative does not exist.
Use the power rule to take the derivative. So f '(x) = 3(6)x(3-1) - 1(18)x(1-1) - 0 = 18x2 - 18
18x2 - 18 = 0
18x2 = 18
x2 = 1
x = 1 and x = -1
There are no values of x where the derivative does not exist so the critical points are x = 1 and x = -1