The number of extreme points of function y = x ^ 4 / 4-x ^ 3 / 3 is

The number of extreme points of function y = x ^ 4 / 4-x ^ 3 / 3 is

y = x^4/4 - x^3/3
y' = x^3 - x^2
=x^2(x-1)
The roots of the derivative of a function are x = 0 and x = 1
When x1, y '> 0
y'(1+) * y'(1-) < 0
So x = 1 is a minimum
Then the number of extreme points is 1