(-5x+3)(-x-4)=0

Solution for (-5x+3)(-x-4)=0 equation:

(-5x+3)(-x-4)=0

We add all the numbers together, and all the variables

(-5x+3)(-1x-4)=0

We multiply parentheses ..

(+5x^2+20x-3x-12)=0

We get rid of parentheses

5x^2+20x-3x-12=0

We add all the numbers together, and all the variables

5x^2+17x-12=0

a = 5; b = 17; c = -12;
Δ = b2-4ac
Δ = 172-4·5·(-12)
Δ = 529
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{529}=23$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(17)-23}{2*5}=\frac{-40}{10}
=-4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(17)+23}{2*5}=\frac{6}{10}
=3/5
$