x2-11x=42

Solution for x2-11x=42 equation:

x2-11x=42

We move all terms to the left:

x2-11x-(42)=0

We add all the numbers together, and all the variables

x^2-11x-42=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:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

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