(10x-9)(-9x-3)=0

Solution for (10x-9)(-9x-3)=0 equation:

(10x-9)(-9x-3)=0

We multiply parentheses ..

(-90x^2-30x+81x+27)=0

We get rid of parentheses

-90x^2-30x+81x+27=0

We add all the numbers together, and all the variables

-90x^2+51x+27=0

a = -90; b = 51; c = +27;
Δ = b2-4ac
Δ = 512-4·(-90)·27
Δ = 12321
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{12321}=111$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(51)-111}{2*-90}=\frac{-162}{-180}
=9/10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(51)+111}{2*-90}=\frac{60}{-180}
=-1/3
$