42-11x=x^2

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

42-11x=x^2

We move all terms to the left:

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

determiningTheFunctionDomain
-x^2-11x+42=0

We add all the numbers together, and all the variables

-1x^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
$