How to do I solve this problem? $3x^2-12=0$

Question

I can't remember how to do these and just need step by step so I can finish the problem. This is only a portion of my calculus problem but I forget how to do this part. The whole problem is f(x) = x^3-12x+17 find the relative extreme points of the function if they exist. I did the first part and found the derivatives of the problem but now I am stuck at the next step which is what I posted for my question. It's been years since I took algebra so I forget. Thanks!

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Answer 1 · 2017-02-03T17:07:39

$x = -2, x = 2$

You need to factor $3x^2-12$ , which ends up being

$3(x+2) (x-2)$

and then set each of these (but ignore the $3$ ) equal to zero and solve.

$x+2=0$

$x+2- 2 = 0 - 2$

$x=-2$

and

$x-2=0$

$x-2+2=0+2$

$x=2$

So $x = 2, -2$