0=81k^2-4

Solution for 0=81k^2-4 equation:

0=81k^2-4

We move all terms to the left:

0-(81k^2-4)=0

We add all the numbers together, and all the variables

-(81k^2-4)=0

We get rid of parentheses

-81k^2+4=0

a = -81; b = 0; c = +4;
Δ = b2-4ac
Δ = 02-4·(-81)·4
Δ = 1296
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1296}=36$
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-36}{2*-81}=\frac{-36}{-162}
=2/9
$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+36}{2*-81}=\frac{36}{-162}
=-2/9
$