(9x-12)(7x+4)=0

Solution for (9x-12)(7x+4)=0 equation:

(9x-12)(7x+4)=0

We multiply parentheses ..

(+63x^2+36x-84x-48)=0

We get rid of parentheses

63x^2+36x-84x-48=0

We add all the numbers together, and all the variables

63x^2-48x-48=0

a = 63; b = -48; c = -48;
Δ = b2-4ac
Δ = -482-4·63·(-48)
Δ = 14400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{14400}=120$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-48)-120}{2*63}=\frac{-72}{126}
=-4/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-48)+120}{2*63}=\frac{168}{126}
=1+1/3
$