-2.5x^2+30x+100=0

Solution for -2.5x^2+30x+100=0 equation:

-2.5x^2+30x+100=0

a = -2.5; b = 30; c = +100;
Δ = b2-4ac
Δ = 302-4·(-2.5)·100
Δ = 1900
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:

$\sqrt{\Delta}=\sqrt{1900}=\sqrt{100*19}=\sqrt{100}*\sqrt{19}=10\sqrt{19}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(30)-10\sqrt{19}}{2*-2.5}=\frac{-30-10\sqrt{19}}{-5}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(30)+10\sqrt{19}}{2*-2.5}=\frac{-30+10\sqrt{19}}{-5}
$