-x^2-6x+26=0

Solution for -x^2-6x+26=0 equation:

-x^2-6x+26=0

We add all the numbers together, and all the variables

-1x^2-6x+26=0

a = -1; b = -6; c = +26;
Δ = b2-4ac
Δ = -62-4·(-1)·26
Δ = 140
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:

$\sqrt{\Delta}=\sqrt{140}=\sqrt{4*35}=\sqrt{4}*\sqrt{35}=2\sqrt{35}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-2\sqrt{35}}{2*-1}=\frac{6-2\sqrt{35}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+2\sqrt{35}}{2*-1}=\frac{6+2\sqrt{35}}{-2}
$