a^2-26a+156=0

Solution for a^2-26a+156=0 equation:

a^2-26a+156=0

a = 1; b = -26; c = +156;
Δ = b2-4ac
Δ = -262-4·1·156
Δ = 52
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{52}=\sqrt{4*13}=\sqrt{4}*\sqrt{13}=2\sqrt{13}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-26)-2\sqrt{13}}{2*1}=\frac{26-2\sqrt{13}}{2}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-26)+2\sqrt{13}}{2*1}=\frac{26+2\sqrt{13}}{2}
$