CALCULUS: STATIONARY POINT

$$f(x)=x^3+Ax+B$$
has a stationary point at (-2, 3). Find the values of A & B.

---
I've already found A=-12. I just don't know how to find B.

Question

CALCULUS: STATIONARY POINT

$$f(x)=x^3+Ax+B$$
has a stationary point at (-2, 3). Find the values of A & B.

---
I've already found A=-12. I just don't know how to find B.

zale101 · Answer

what does it mean if the function has a stationary point?

zale101 · Answer

Stationary point means the derivative of that function is zero.

anonymous · Answer

Well, I just know that if a function has a stationary point then the derivative of that function is equal to 0.

anonymous · Answer

oh... you already said that lol

zale101 · Answer

Did you find b already or not?

anonymous · Answer

Nope, not yet.

anonymous · Answer

I don't know what to do.

anonymous · Answer

Should I just plug in (2,3) to the function to solve for B?

anonymous · Answer

If so, then I'll get B=-13. But I'm not sure.

anonymous · Answer

this is not just about plugging in values
you need to know what you're doing and why you're doing it

anonymous · Answer

Yeah, that's why I am asking how to do it. :)

zale101 · Answer

You should start with taking the derivative, set it equal to zero

anonymous · Answer

how should not be the point of interest

anonymous · Answer

Okay, I'll show my work.

zale101 · Answer

set x=-2 and f(x) =3

anonymous · Answer

^ that's what I did to find B.

anonymous · Answer

|dw:1442978733930:dw|