-5x2+30x+12=0

Solution for -5x2+30x+12=0 equation:

-5x^2+30x+12=0

a = -5; b = 30; c = +12;
Δ = b2-4ac
Δ = 302-4·(-5)·12
Δ = 1140
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:

$\sqrt{\Delta}=\sqrt{1140}=\sqrt{4*285}=\sqrt{4}*\sqrt{285}=2\sqrt{285}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(30)-2\sqrt{285}}{2*-5}=\frac{-30-2\sqrt{285}}{-10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(30)+2\sqrt{285}}{2*-5}=\frac{-30+2\sqrt{285}}{-10}
$