What is the mistake in solving this derivative?

[bk1]

Hi everyone,

I'm having trouble solving this one. I just don't really see what I'm doing wrong.

Homework Statement

X² - x - 2
X² + 5x + 6

Homework Equations

The Attempt at a Solution

(( x-1 ) * x² + 5x + 6 ) - (( x + 5 ) * x²-x-2 )
( x² + 5x + 6)²

So 8x² -6x-16
(x² + 5x + 6)²

Now I know this isn't the correct awnser. Because it should say
6x² + 16x + 4
( x² + 5x+6)²

Could anyone point out to me what I'm doing wrong?
Thanks in advance.
Tim

 

[irycio]

The derivative of x^2 is 2x, not x.