(9x-1)(8x+4)=0

Solution for (9x-1)(8x+4)=0 equation:

(9x-1)(8x+4)=0

We multiply parentheses ..

(+72x^2+36x-8x-4)=0

We get rid of parentheses

72x^2+36x-8x-4=0

We add all the numbers together, and all the variables

72x^2+28x-4=0

a = 72; b = 28; c = -4;
Δ = b2-4ac
Δ = 282-4·72·(-4)
Δ = 1936
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1936}=44$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(28)-44}{2*72}=\frac{-72}{144}
=-1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+44}{2*72}=\frac{16}{144}
=1/9
$