-x*x-25x=-300

Solution for -x*x-25x=-300 equation:

-x*x-25x=-300

We move all terms to the left:

-x*x-25x-(-300)=0

We add all the numbers together, and all the variables

-25x-x*x+300=0

Wy multiply elements

-1x^2-25x+300=0

a = -1; b = -25; c = +300;
Δ = b2-4ac
Δ = -252-4·(-1)·300
Δ = 1825
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:

$\sqrt{\Delta}=\sqrt{1825}=\sqrt{25*73}=\sqrt{25}*\sqrt{73}=5\sqrt{73}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-25)-5\sqrt{73}}{2*-1}=\frac{25-5\sqrt{73}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-25)+5\sqrt{73}}{2*-1}=\frac{25+5\sqrt{73}}{-2}
$