X(x+20)=156

Solution for X(x+20)=156 equation:

X(X+20)=156

We move all terms to the left:

X(X+20)-(156)=0

We multiply parentheses

X^2+20X-156=0

a = 1; b = 20; c = -156;
Δ = b2-4ac
Δ = 202-4·1·(-156)
Δ = 1024
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1024}=32$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-32}{2*1}=\frac{-52}{2}
=-26
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+32}{2*1}=\frac{12}{2}
=6
$