Question

I just want to double check if I'm right?
f(x)=-x^4-4 turning point
The turning point for this is 0 right?

Answer 1

A turning point is a point at which the derivative changes sign.
So calculate f'(x) and solve f'(x)=0. Then put the solutions on the number line. Check the sign of f' between the solutions to obtain a sign scheme of f'. YOu've found the turning points if the sign of f'changes when passing a solution of f'(x)=0.

Answer 2

So...

f'(x)=-4x³

Solve f'(x)=0: -4x³=0, so x=0. There are no more solutions.



Turning point: yes, it's zero!

Answer 3

thank you very much

Answer 4

Sorry, the sign scheme shifted a little to the left, but you've got the point...