0.81x^2=90

Solution for 0.81x^2=90 equation:

0.81x^2=90

We move all terms to the left:

0.81x^2-(90)=0

a = 0.81; b = 0; c = -90;
Δ = b2-4ac
Δ = 02-4·0.81·(-90)
Δ = 291.6
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-\sqrt{291.6}}{2*0.81}=\frac{0-\sqrt{291.6}}{1.62}
=-\frac{\sqrt{}}{1.62}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{291.6}}{2*0.81}=\frac{0+\sqrt{291.6}}{1.62}
=\frac{\sqrt{}}{1.62}
$