a^2-42=11a

Solution for a^2-42=11a equation:

a^2-42=11a

We move all terms to the left:

a^2-42-(11a)=0

a = 1; b = -11; c = -42;
Δ = b2-4ac
Δ = -112-4·1·(-42)
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-11)-17}{2*1}=\frac{-6}{2}
=-3
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-11)+17}{2*1}=\frac{28}{2}
=14
$