3(x^2-81)=0

Solution for 3(x^2-81)=0 equation:

3(x^2-81)=0

We multiply parentheses

3x^2-243=0

a = 3; b = 0; c = -243;
Δ = b2-4ac
Δ = 02-4·3·(-243)
Δ = 2916
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2916}=54$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-54}{2*3}=\frac{-54}{6}
=-9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+54}{2*3}=\frac{54}{6}
=9
$