(x+70)(x+20)=180

Solution for (x+70)(x+20)=180 equation:

(x+70)(x+20)=180

We move all terms to the left:

(x+70)(x+20)-(180)=0

We multiply parentheses ..

(+x^2+20x+70x+1400)-180=0

We get rid of parentheses

x^2+20x+70x+1400-180=0

We add all the numbers together, and all the variables

x^2+90x+1220=0

a = 1; b = 90; c = +1220;
Δ = b2-4ac
Δ = 902-4·1·1220
Δ = 3220
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:

$\sqrt{\Delta}=\sqrt{3220}=\sqrt{4*805}=\sqrt{4}*\sqrt{805}=2\sqrt{805}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(90)-2\sqrt{805}}{2*1}=\frac{-90-2\sqrt{805}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(90)+2\sqrt{805}}{2*1}=\frac{-90+2\sqrt{805}}{2}
$