(5x-40)(8x-80)=0

Solution for (5x-40)(8x-80)=0 equation:

(5x-40)(8x-80)=0

We multiply parentheses ..

(+40x^2-400x-320x+3200)=0

We get rid of parentheses

40x^2-400x-320x+3200=0

We add all the numbers together, and all the variables

40x^2-720x+3200=0

a = 40; b = -720; c = +3200;
Δ = b2-4ac
Δ = -7202-4·40·3200
Δ = 6400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6400}=80$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-720)-80}{2*40}=\frac{640}{80}
=8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-720)+80}{2*40}=\frac{800}{80}
=10
$