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

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

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

We multiply parentheses ..

(+36x^2+16x-9x-4)=0

We get rid of parentheses

36x^2+16x-9x-4=0

We add all the numbers together, and all the variables

36x^2+7x-4=0

a = 36; b = 7; c = -4;
Δ = b2-4ac
Δ = 72-4·36·(-4)
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-25}{2*36}=\frac{-32}{72}
=-4/9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+25}{2*36}=\frac{18}{72}
=1/4
$