(x+4)(-x+2)=8

Solution for (x+4)(-x+2)=8 equation:

(x+4)(-x+2)=8

We move all terms to the left:

(x+4)(-x+2)-(8)=0

We add all the numbers together, and all the variables

(x+4)(-1x+2)-8=0

We multiply parentheses ..

(-1x^2+2x-4x+8)-8=0

We get rid of parentheses

-1x^2+2x-4x+8-8=0

We add all the numbers together, and all the variables

-1x^2-2x=0

a = -1; b = -2; c = 0;
Δ = b2-4ac
Δ = -22-4·(-1)·0
Δ = 4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4}=2$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-2}{2*-1}=\frac{0}{-2}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+2}{2*-1}=\frac{4}{-2}
=-2
$