-x^2+18x=56

Solution for -x^2+18x=56 equation:

-x^2+18x=56

We move all terms to the left:

-x^2+18x-(56)=0

We add all the numbers together, and all the variables

-1x^2+18x-56=0

a = -1; b = 18; c = -56;
Δ = b2-4ac
Δ = 182-4·(-1)·(-56)
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(18)-10}{2*-1}=\frac{-28}{-2}
=+14
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(18)+10}{2*-1}=\frac{-8}{-2}
=+4
$