X(x+12)=100

Solution for X(x+12)=100 equation:

X(X+12)=100

We move all terms to the left:

X(X+12)-(100)=0

We multiply parentheses

X^2+12X-100=0

a = 1; b = 12; c = -100;
Δ = b2-4ac
Δ = 122-4·1·(-100)
Δ = 544
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{544}=\sqrt{16*34}=\sqrt{16}*\sqrt{34}=4\sqrt{34}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-4\sqrt{34}}{2*1}=\frac{-12-4\sqrt{34}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+4\sqrt{34}}{2*1}=\frac{-12+4\sqrt{34}}{2}
$