-x^2-16x+225=0

Solution for -x^2-16x+225=0 equation:

-x^2-16x+225=0

We add all the numbers together, and all the variables

-1x^2-16x+225=0

a = -1; b = -16; c = +225;
Δ = b2-4ac
Δ = -162-4·(-1)·225
Δ = 1156
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1156}=34$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-34}{2*-1}=\frac{-18}{-2}
=+9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+34}{2*-1}=\frac{50}{-2}
=-25
$