(5x)(4x+10)=180

Solution for (5x)(4x+10)=180 equation:

(5x)(4x+10)=180

We move all terms to the left:

(5x)(4x+10)-(180)=0

We multiply parentheses

20x^2+50x-180=0

a = 20; b = 50; c = -180;
Δ = b2-4ac
Δ = 502-4·20·(-180)
Δ = 16900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{16900}=130$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(50)-130}{2*20}=\frac{-180}{40}
=-4+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(50)+130}{2*20}=\frac{80}{40}
=2
$