d^2=10d+2

Solution for d^2=10d+2 equation:

d^2=10d+2

We move all terms to the left:

d^2-(10d+2)=0

We get rid of parentheses

d^2-10d-2=0

a = 1; b = -10; c = -2;
Δ = b2-4ac
Δ = -102-4·1·(-2)
Δ = 108
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:

$\sqrt{\Delta}=\sqrt{108}=\sqrt{36*3}=\sqrt{36}*\sqrt{3}=6\sqrt{3}$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-6\sqrt{3}}{2*1}=\frac{10-6\sqrt{3}}{2}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+6\sqrt{3}}{2*1}=\frac{10+6\sqrt{3}}{2}
$