(4x+7)(9x-8)=0

Solution for (4x+7)(9x-8)=0 equation:

(4x+7)(9x-8)=0

We multiply parentheses ..

(+36x^2-32x+63x-56)=0

We get rid of parentheses

36x^2-32x+63x-56=0

We add all the numbers together, and all the variables

36x^2+31x-56=0

a = 36; b = 31; c = -56;
Δ = b2-4ac
Δ = 312-4·36·(-56)
Δ = 9025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9025}=95$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(31)-95}{2*36}=\frac{-126}{72}
=-1+3/4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(31)+95}{2*36}=\frac{64}{72}
=8/9
$