0=-x^2+15x+250

Solution for 0=-x^2+15x+250 equation:

0=-x^2+15x+250

We move all terms to the left:

0-(-x^2+15x+250)=0

We add all the numbers together, and all the variables

-(-x^2+15x+250)=0

We get rid of parentheses

x^2-15x-250=0

a = 1; b = -15; c = -250;
Δ = b2-4ac
Δ = -152-4·1·(-250)
Δ = 1225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1225}=35$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-35}{2*1}=\frac{-20}{2}
=-10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+35}{2*1}=\frac{50}{2}
=25
$