y^2-28y+26=0

Solution for y^2-28y+26=0 equation:

y^2-28y+26=0

a = 1; b = -28; c = +26;
Δ = b2-4ac
Δ = -282-4·1·26
Δ = 680
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{680}=\sqrt{4*170}=\sqrt{4}*\sqrt{170}=2\sqrt{170}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-28)-2\sqrt{170}}{2*1}=\frac{28-2\sqrt{170}}{2}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-28)+2\sqrt{170}}{2*1}=\frac{28+2\sqrt{170}}{2}
$