-4(x+3)5x=15

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

-4(x+3)5x=15

We move all terms to the left:

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

We multiply parentheses

-20x^2-60x-15=0

a = -20; b = -60; c = -15;
Δ = b2-4ac
Δ = -602-4·(-20)·(-15)
Δ = 2400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2400}=\sqrt{400*6}=\sqrt{400}*\sqrt{6}=20\sqrt{6}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-20\sqrt{6}}{2*-20}=\frac{60-20\sqrt{6}}{-40}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+20\sqrt{6}}{2*-20}=\frac{60+20\sqrt{6}}{-40}
$