Unit 2, question about derivatives

[lolaishappy]

Im new here, and I always need help 
so this is the question..

The function y=x^3(a/3) - x^2(b/2) + 6x + c  has turning points at x=1 and x=-1.
A) find the derivative..
which is    ax^2 -bx + 6

B) Find the values of a and b. Im stuck at this question 

[theshunpo]

At the turning points (x=1 and x=-1) (the derivative) is equal to 0.

Using x=1 and x=-1, you can create two simultaneous equations which equal to 0, which will allow you to solve for a and b.
These simultaneous equations are:

Spoiler

a-b+6=0 and a+b+6=0

[lolaishappy]

At the turning points (x=1 and x=-1) (the derivative) is equal to 0.

Using x=1 and x=-1, you can create two simultaneous equations which equal to 0, which will allow you to solve for a and b.
These simultaneous equations are:

Spoiler

a-b+6=0 and a+b+6=0

Thanks so much, much simpler than the teacher's way.