(X)=x^2+8x-20

Solution for (X)=x^2+8x-20 equation:

(X)=X^2+8X-20

We move all terms to the left:

(X)-(X^2+8X-20)=0

We get rid of parentheses

-X^2+X-8X+20=0

We add all the numbers together, and all the variables

-1X^2-7X+20=0

a = -1; b = -7; c = +20;
Δ = b2-4ac
Δ = -72-4·(-1)·20
Δ = 129
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-\sqrt{129}}{2*-1}=\frac{7-\sqrt{129}}{-2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+\sqrt{129}}{2*-1}=\frac{7+\sqrt{129}}{-2}
$