-(4x+9)*(7x-9)=0

Solution for -(4x+9)*(7x-9)=0 equation:

-(4x+9)(7x-9)=0

We multiply parentheses ..

-(+28x^2-36x+63x-81)=0

We get rid of parentheses

-28x^2+36x-63x+81=0

We add all the numbers together, and all the variables

-28x^2-27x+81=0

a = -28; b = -27; c = +81;
Δ = b2-4ac
Δ = -272-4·(-28)·81
Δ = 9801
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9801}=99$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-27)-99}{2*-28}=\frac{-72}{-56}
=1+2/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-27)+99}{2*-28}=\frac{126}{-56}
=-2+1/4
$