(-5+4x)(-15+3x)=0

Solution for (-5+4x)(-15+3x)=0 equation:

(-5+4x)(-15+3x)=0

We add all the numbers together, and all the variables

(4x-5)(3x-15)=0

We multiply parentheses ..

(+12x^2-60x-15x+75)=0

We get rid of parentheses

12x^2-60x-15x+75=0

We add all the numbers together, and all the variables

12x^2-75x+75=0

a = 12; b = -75; c = +75;
Δ = b2-4ac
Δ = -752-4·12·75
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-75)-45}{2*12}=\frac{30}{24}
=1+1/4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-75)+45}{2*12}=\frac{120}{24}
=5
$