5x-5x(2x-7)=0

Solution for 5x-5x(2x-7)=0 equation:

5x-5x(2x-7)=0

We multiply parentheses

-10x^2+5x+35x=0

We add all the numbers together, and all the variables

-10x^2+40x=0

a = -10; b = 40; c = 0;
Δ = b2-4ac
Δ = 402-4·(-10)·0
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-40}{2*-10}=\frac{-80}{-20}
=+4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+40}{2*-10}=\frac{0}{-20}
=0
$