100=81x2

Solution for 100=81x2 equation:

100=81x^2

We move all terms to the left:

100-(81x^2)=0

a = -81; b = 0; c = +100;
Δ = b2-4ac
Δ = 02-4·(-81)·100
Δ = 32400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{32400}=180$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-180}{2*-81}=\frac{-180}{-162}
=1+1/9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+180}{2*-81}=\frac{180}{-162}
=-1+1/9
$