x(x+8)=5

Solution for x(x+8)=5 equation:

x(x+8)=5

We move all terms to the left:

x(x+8)-(5)=0

We multiply parentheses

x^2+8x-5=0

a = 1; b = 8; c = -5;
Δ = b2-4ac
Δ = 82-4·1·(-5)
Δ = 84
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{84}=\sqrt{4*21}=\sqrt{4}*\sqrt{21}=2\sqrt{21}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-2\sqrt{21}}{2*1}=\frac{-8-2\sqrt{21}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+2\sqrt{21}}{2*1}=\frac{-8+2\sqrt{21}}{2}
$