20.77=x^2+3.6x

Solution for 20.77=x^2+3.6x equation:

20.77=x^2+3.6x

We move all terms to the left:

20.77-(x^2+3.6x)=0

We get rid of parentheses

-x^2-3.6x+20.77=0

We add all the numbers together, and all the variables

-1x^2-3.6x+20.77=0

a = -1; b = -3.6; c = +20.77;
Δ = b2-4ac
Δ = -3.62-4·(-1)·20.77
Δ = 96.04
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3.6)-\sqrt{96.04}}{2*-1}=\frac{3.6-\sqrt{96.04}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3.6)+\sqrt{96.04}}{2*-1}=\frac{3.6+\sqrt{96.04}}{-2}
$