x^2-9x^2+81=0

Solution for x^2-9x^2+81=0 equation:

x^2-9x^2+81=0

We add all the numbers together, and all the variables

-8x^2+81=0

a = -8; b = 0; c = +81;
Δ = b2-4ac
Δ = 02-4·(-8)·81
Δ = 2592
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2592}=\sqrt{1296*2}=\sqrt{1296}*\sqrt{2}=36\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-36\sqrt{2}}{2*-8}=\frac{0-36\sqrt{2}}{-16}
=-\frac{36\sqrt{2}}{-16}
=-\frac{9\sqrt{2}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+36\sqrt{2}}{2*-8}=\frac{0+36\sqrt{2}}{-16}
=\frac{36\sqrt{2}}{-16}
=\frac{9\sqrt{2}}{-4}
$