-x2+12x-20=0

Solution for -x2+12x-20=0 equation:

-x2+12x-20=0

We add all the numbers together, and all the variables

-1x^2+12x-20=0

a = -1; b = 12; c = -20;
Δ = b2-4ac
Δ = 122-4·(-1)·(-20)
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-8}{2*-1}=\frac{-20}{-2}
=+10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+8}{2*-1}=\frac{-4}{-2}
=+2
$