15x(x+3)=60

Solution for 15x(x+3)=60 equation:

15x(x+3)=60

We move all terms to the left:

15x(x+3)-(60)=0

We multiply parentheses

15x^2+45x-60=0

a = 15; b = 45; c = -60;
Δ = b2-4ac
Δ = 452-4·15·(-60)
Δ = 5625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5625}=75$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(45)-75}{2*15}=\frac{-120}{30}
=-4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(45)+75}{2*15}=\frac{30}{30}
=1
$