X(-15x-5)=-120

Solution for X(-15x-5)=-120 equation:

X(-15X-5)=-120

We move all terms to the left:

X(-15X-5)-(-120)=0

We add all the numbers together, and all the variables

X(-15X-5)+120=0

We multiply parentheses

-15X^2-5X+120=0

a = -15; b = -5; c = +120;
Δ = b2-4ac
Δ = -52-4·(-15)·120
Δ = 7225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{7225}=85$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-85}{2*-15}=\frac{-80}{-30}
=2+2/3
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+85}{2*-15}=\frac{90}{-30}
=-3
$