How to judge the monotone interval of Y '= 10x ^ 3-9x = 0 after solving the three extreme points?

How to judge the monotone interval of Y '= 10x ^ 3-9x = 0 after solving the three extreme points?

The three extremum points are divided into four intervals. In each interval, take a special value (take a good value) and substitute it into y ', if it is greater than 0, it will increase, otherwise it will decrease