80=(4x+4)x

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

80=(4x+4)x

We move all terms to the left:

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


We calculate terms in parentheses: -((4x+4)x), so:

(4x+4)x

We multiply parentheses

4x^2+4x

Back to the equation:

-(4x^2+4x)


We get rid of parentheses

-4x^2-4x+80=0

a = -4; b = -4; c = +80;
Δ = b2-4ac
Δ = -42-4·(-4)·80
Δ = 1296
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1296}=36$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-36}{2*-4}=\frac{-32}{-8}
=+4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+36}{2*-4}=\frac{40}{-8}
=-5
$