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

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

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

We add all the numbers together, and all the variables

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

We multiply parentheses

4x^2+4x^2+(-2x+7)(-2x+5)-10x-14x=0

We multiply parentheses ..

4x^2+4x^2+(+4x^2-10x-14x+35)-10x-14x=0

We add all the numbers together, and all the variables

8x^2+(+4x^2-10x-14x+35)-24x=0

We get rid of parentheses

8x^2+4x^2-10x-14x-24x+35=0

We add all the numbers together, and all the variables

12x^2-48x+35=0

a = 12; b = -48; c = +35;
Δ = b2-4ac
Δ = -482-4·12·35
Δ = 624
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{624}=\sqrt{16*39}=\sqrt{16}*\sqrt{39}=4\sqrt{39}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-48)-4\sqrt{39}}{2*12}=\frac{48-4\sqrt{39}}{24}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-48)+4\sqrt{39}}{2*12}=\frac{48+4\sqrt{39}}{24}
$