(7-2x)(9-2x)-35=0

Solution for (7-2x)(9-2x)-35=0 equation:

(7-2x)(9-2x)-35=0

We add all the numbers together, and all the variables

(-2x+7)(-2x+9)-35=0

We multiply parentheses ..

(+4x^2-18x-14x+63)-35=0

We get rid of parentheses

4x^2-18x-14x+63-35=0

We add all the numbers together, and all the variables

4x^2-32x+28=0

a = 4; b = -32; c = +28;
Δ = b2-4ac
Δ = -322-4·4·28
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-32)-24}{2*4}=\frac{8}{8}
=1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-32)+24}{2*4}=\frac{56}{8}
=7
$