15x(13x+5)=120

Solution for 15x(13x+5)=120 equation:

15x(13x+5)=120

We move all terms to the left:

15x(13x+5)-(120)=0

We multiply parentheses

195x^2+75x-120=0

a = 195; b = 75; c = -120;
Δ = b2-4ac
Δ = 752-4·195·(-120)
Δ = 99225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{99225}=315$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(75)-315}{2*195}=\frac{-390}{390}
=-1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(75)+315}{2*195}=\frac{240}{390}
=8/13
$