2x(x+15)=80

Solution for 2x(x+15)=80 equation:

2x(x+15)=80

We move all terms to the left:

2x(x+15)-(80)=0

We multiply parentheses

2x^2+30x-80=0

a = 2; b = 30; c = -80;
Δ = b2-4ac
Δ = 302-4·2·(-80)
Δ = 1540
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:

$\sqrt{\Delta}=\sqrt{1540}=\sqrt{4*385}=\sqrt{4}*\sqrt{385}=2\sqrt{385}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(30)-2\sqrt{385}}{2*2}=\frac{-30-2\sqrt{385}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(30)+2\sqrt{385}}{2*2}=\frac{-30+2\sqrt{385}}{4}
$