3x^=81-x^2

Solution for 3x^=81-x^2 equation:

3x^=81-x^2

We move all terms to the left:

3x^-(81-x^2)=0

We add all the numbers together, and all the variables

-(81-x^2)+3x=0

We get rid of parentheses

x^2+3x-81=0

a = 1; b = 3; c = -81;
Δ = b2-4ac
Δ = 32-4·1·(-81)
Δ = 333
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:

$\sqrt{\Delta}=\sqrt{333}=\sqrt{9*37}=\sqrt{9}*\sqrt{37}=3\sqrt{37}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(3)-3\sqrt{37}}{2*1}=\frac{-3-3\sqrt{37}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+3\sqrt{37}}{2*1}=\frac{-3+3\sqrt{37}}{2}
$