0=x^2-21x+26

Solution for 0=x^2-21x+26 equation:

0=x^2-21x+26

We move all terms to the left:

0-(x^2-21x+26)=0

We add all the numbers together, and all the variables

-(x^2-21x+26)=0

We get rid of parentheses

-x^2+21x-26=0

We add all the numbers together, and all the variables

-1x^2+21x-26=0

a = -1; b = 21; c = -26;
Δ = b2-4ac
Δ = 212-4·(-1)·(-26)
Δ = 337
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-\sqrt{337}}{2*-1}=\frac{-21-\sqrt{337}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+\sqrt{337}}{2*-1}=\frac{-21+\sqrt{337}}{-2}
$