(5x+5)(3x+15)=180

Solution for (5x+5)(3x+15)=180 equation:

(5x+5)(3x+15)=180

We move all terms to the left:

(5x+5)(3x+15)-(180)=0

We multiply parentheses ..

(+15x^2+75x+15x+75)-180=0

We get rid of parentheses

15x^2+75x+15x+75-180=0

We add all the numbers together, and all the variables

15x^2+90x-105=0

a = 15; b = 90; c = -105;
Δ = b2-4ac
Δ = 902-4·15·(-105)
Δ = 14400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{14400}=120$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(90)-120}{2*15}=\frac{-210}{30}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(90)+120}{2*15}=\frac{30}{30}
=1
$