-7x^2+12x+20=0

Solution for -7x^2+12x+20=0 equation:

-7x^2+12x+20=0

a = -7; b = 12; c = +20;
Δ = b2-4ac
Δ = 122-4·(-7)·20
Δ = 704
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:

$\sqrt{\Delta}=\sqrt{704}=\sqrt{64*11}=\sqrt{64}*\sqrt{11}=8\sqrt{11}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-8\sqrt{11}}{2*-7}=\frac{-12-8\sqrt{11}}{-14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+8\sqrt{11}}{2*-7}=\frac{-12+8\sqrt{11}}{-14}
$