(d+8)(d+8)=5

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

(d+8)(d+8)=5

We move all terms to the left:

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

We multiply parentheses ..

(+d^2+8d+8d+64)-5=0

We get rid of parentheses

d^2+8d+8d+64-5=0

We add all the numbers together, and all the variables

d^2+16d+59=0

a = 1; b = 16; c = +59;
Δ = b2-4ac
Δ = 162-4·1·59
Δ = 20
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{20}=\sqrt{4*5}=\sqrt{4}*\sqrt{5}=2\sqrt{5}$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(16)-2\sqrt{5}}{2*1}=\frac{-16-2\sqrt{5}}{2}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(16)+2\sqrt{5}}{2*1}=\frac{-16+2\sqrt{5}}{2}
$