-25x^2+30x+100=0

Solution for -25x^2+30x+100=0 equation:

-25x^2+30x+100=0

a = -25; b = 30; c = +100;
Δ = b2-4ac
Δ = 302-4·(-25)·100
Δ = 10900
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:

$\sqrt{\Delta}=\sqrt{10900}=\sqrt{100*109}=\sqrt{100}*\sqrt{109}=10\sqrt{109}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(30)-10\sqrt{109}}{2*-25}=\frac{-30-10\sqrt{109}}{-50}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(30)+10\sqrt{109}}{2*-25}=\frac{-30+10\sqrt{109}}{-50}
$