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Simplifying
9r2 + -81 = 0
Reorder the terms:
-81 + 9r2 = 0
Solving
-81 + 9r2 = 0
Solving for variable 'r'.
Move all terms containing r to the left, all other terms to the right.
Add '81' to each side of the equation.
-81 + 81 + 9r2 = 0 + 81
Combine like terms: -81 + 81 = 0
0 + 9r2 = 0 + 81
9r2 = 0 + 81
Combine like terms: 0 + 81 = 81
9r2 = 81
Divide each side by '9'.
r2 = 9
Simplifying
r2 = 9
Take the square root of each side:
r = {-3, 3}
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