3r^2=81+r^2

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Solution for 3r^2=81+r^2 equation: 


Simplifying
3r2 = 81 + r2

Solving
3r2 = 81 + r2

Solving for variable 'r'.

Move all terms containing r to the left, all other terms to the right.

Add '-1r2' to each side of the equation.
3r2 + -1r2 = 81 + r2 + -1r2

Combine like terms: 3r2 + -1r2 = 2r2
2r2 = 81 + r2 + -1r2

Combine like terms: r2 + -1r2 = 0
2r2 = 81 + 0
2r2 = 81

Divide each side by '2'.
r2 = 40.5

Simplifying
r2 = 40.5

Take the square root of each side:
r = {-6.363961031, 6.363961031}

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