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

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

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

We multiply parentheses ..

(+63x^2+36x-28x-16)=0

We get rid of parentheses

63x^2+36x-28x-16=0

We add all the numbers together, and all the variables

63x^2+8x-16=0

a = 63; b = 8; c = -16;
Δ = b2-4ac
Δ = 82-4·63·(-16)
Δ = 4096
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4096}=64$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-64}{2*63}=\frac{-72}{126}
=-4/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+64}{2*63}=\frac{56}{126}
=4/9
$