(-5x-9)(-4x-1)=0

Solution for (-5x-9)(-4x-1)=0 equation:

(-5x-9)(-4x-1)=0

We multiply parentheses ..

(+20x^2+5x+36x+9)=0

We get rid of parentheses

20x^2+5x+36x+9=0

We add all the numbers together, and all the variables

20x^2+41x+9=0

a = 20; b = 41; c = +9;
Δ = b2-4ac
Δ = 412-4·20·9
Δ = 961
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{961}=31$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(41)-31}{2*20}=\frac{-72}{40}
=-1+4/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(41)+31}{2*20}=\frac{-10}{40}
=-1/4
$