X=x^2+16x+15

Solution for X=x^2+16x+15 equation:

X=X^2+16X+15

We move all terms to the left:

X-(X^2+16X+15)=0

We get rid of parentheses

-X^2+X-16X-15=0

We add all the numbers together, and all the variables

-1X^2-15X-15=0

a = -1; b = -15; c = -15;
Δ = b2-4ac
Δ = -152-4·(-1)·(-15)
Δ = 165
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{165}}{2*-1}=\frac{15-\sqrt{165}}{-2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+\sqrt{165}}{2*-1}=\frac{15+\sqrt{165}}{-2}
$