(2x-7x)(8x-4)=0

Solution for (2x-7x)(8x-4)=0 equation:

(2x-7x)(8x-4)=0

We add all the numbers together, and all the variables

(-5x)(8x-4)=0

We multiply parentheses ..

(-40x^2+20x)=0

We get rid of parentheses

-40x^2+20x=0

a = -40; b = 20; c = 0;
Δ = b2-4ac
Δ = 202-4·(-40)·0
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-20}{2*-40}=\frac{-40}{-80}
=1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+20}{2*-40}=\frac{0}{-80}
=0
$