(9x-9)(7x+1)=0

Solution for (9x-9)(7x+1)=0 equation:

(9x-9)(7x+1)=0

We multiply parentheses ..

(+63x^2+9x-63x-9)=0

We get rid of parentheses

63x^2+9x-63x-9=0

We add all the numbers together, and all the variables

63x^2-54x-9=0

a = 63; b = -54; c = -9;
Δ = b2-4ac
Δ = -542-4·63·(-9)
Δ = 5184
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5184}=72$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-54)-72}{2*63}=\frac{-18}{126}
=-1/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-54)+72}{2*63}=\frac{126}{126}
=1
$