81d^2-64=0

Solution for 81d^2-64=0 equation:

81d^2-64=0

a = 81; b = 0; c = -64;
Δ = b2-4ac
Δ = 02-4·81·(-64)
Δ = 20736
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{20736}=144$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-144}{2*81}=\frac{-144}{162}
=-8/9
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+144}{2*81}=\frac{144}{162}
=8/9
$