Simplify x2+x−12−x2−4x+21÷x+4x+7
First, we have to apply the fraction rule, turning it into (x2+x-12)/(-x2-3x+21)(x+7)/(x+4)
We simplify it to be -(x+4)/(x+7)(x+7)/(x+4)
We multiply it to -(x+7)/(x+7)
Simplify that to be -1
Yay!