# How do you use the first derivative test to determine whether the critical point is a local maximum, local minimum, or neither for #y=x^4 - 8x^2#?

##### 1 Answer

Mar 28, 2015

Second, set it equal to zero;

you get:

and so:

This gives you the critical points (where the inclination of your curve changes).

Third set your derivative >0, and study the combined signs of the derivatives: