x^2-40x+391=0

Solution for x^2-40x+391=0 equation:

x^2-40x+391=0

a = 1; b = -40; c = +391;
Δ = b2-4ac
Δ = -402-4·1·391
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-40)-6}{2*1}=\frac{34}{2}
=17
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-40)+6}{2*1}=\frac{46}{2}
=23
$