-4x+5x(3x+15)=-20

Solution for -4x+5x(3x+15)=-20 equation:

-4x+5x(3x+15)=-20

We move all terms to the left:

-4x+5x(3x+15)-(-20)=0

We add all the numbers together, and all the variables

-4x+5x(3x+15)+20=0

We multiply parentheses

15x^2-4x+75x+20=0

We add all the numbers together, and all the variables

15x^2+71x+20=0

a = 15; b = 71; c = +20;
Δ = b2-4ac
Δ = 712-4·15·20
Δ = 3841
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(71)-\sqrt{3841}}{2*15}=\frac{-71-\sqrt{3841}}{30}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(71)+\sqrt{3841}}{2*15}=\frac{-71+\sqrt{3841}}{30}
$