(x+15)x=8^2

Solution for (x+15)x=8^2 equation:

(x+15)x=8^2

We move all terms to the left:

(x+15)x-(8^2)=0

We add all the numbers together, and all the variables

(x+15)x-64=0

We multiply parentheses

x^2+15x-64=0

a = 1; b = 15; c = -64;
Δ = b2-4ac
Δ = 152-4·1·(-64)
Δ = 481
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{-(15)-\sqrt{481}}{2*1}=\frac{-15-\sqrt{481}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+\sqrt{481}}{2*1}=\frac{-15+\sqrt{481}}{2}
$