-8+x^2=7x+20

Solution for -8+x^2=7x+20 equation:

-8+x^2=7x+20

We move all terms to the left:

-8+x^2-(7x+20)=0

We get rid of parentheses

x^2-7x-20-8=0

We add all the numbers together, and all the variables

x^2-7x-28=0

a = 1; b = -7; c = -28;
Δ = b2-4ac
Δ = -72-4·1·(-28)
Δ = 161
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{-(-7)-\sqrt{161}}{2*1}=\frac{7-\sqrt{161}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+\sqrt{161}}{2*1}=\frac{7+\sqrt{161}}{2}
$