x^2+26x-81=0

Solution for x^2+26x-81=0 equation:

x^2+26x-81=0

a = 1; b = 26; c = -81;
Δ = b2-4ac
Δ = 262-4·1·(-81)
Δ = 1000
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:

$\sqrt{\Delta}=\sqrt{1000}=\sqrt{100*10}=\sqrt{100}*\sqrt{10}=10\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(26)-10\sqrt{10}}{2*1}=\frac{-26-10\sqrt{10}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(26)+10\sqrt{10}}{2*1}=\frac{-26+10\sqrt{10}}{2}
$