(2x-20)(x+15)=180

Solution for (2x-20)(x+15)=180 equation:

(2x-20)(x+15)=180

We move all terms to the left:

(2x-20)(x+15)-(180)=0

We multiply parentheses ..

(+2x^2+30x-20x-300)-180=0

We get rid of parentheses

2x^2+30x-20x-300-180=0

We add all the numbers together, and all the variables

2x^2+10x-480=0

a = 2; b = 10; c = -480;
Δ = b2-4ac
Δ = 102-4·2·(-480)
Δ = 3940
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:

$\sqrt{\Delta}=\sqrt{3940}=\sqrt{4*985}=\sqrt{4}*\sqrt{985}=2\sqrt{985}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-2\sqrt{985}}{2*2}=\frac{-10-2\sqrt{985}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+2\sqrt{985}}{2*2}=\frac{-10+2\sqrt{985}}{4}
$