4x(10x+80)=360

Solution for 4x(10x+80)=360 equation:

4x(10x+80)=360

We move all terms to the left:

4x(10x+80)-(360)=0

We multiply parentheses

40x^2+320x-360=0

a = 40; b = 320; c = -360;
Δ = b2-4ac
Δ = 3202-4·40·(-360)
Δ = 160000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{160000}=400$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(320)-400}{2*40}=\frac{-720}{80}
=-9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(320)+400}{2*40}=\frac{80}{80}
=1
$