(9x+7)(5x-5)=0

Solution for (9x+7)(5x-5)=0 equation:

(9x+7)(5x-5)=0

We multiply parentheses ..

(+45x^2-45x+35x-35)=0

We get rid of parentheses

45x^2-45x+35x-35=0

We add all the numbers together, and all the variables

45x^2-10x-35=0

a = 45; b = -10; c = -35;
Δ = b2-4ac
Δ = -102-4·45·(-35)
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{-(-10)-80}{2*45}=\frac{-70}{90}
=-7/9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+80}{2*45}=\frac{90}{90}
=1
$