You can put this solution on YOUR website! r^3=3r^2-54r
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r^3 - 3r^2 + 54r = 0
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Factor:
r(r^2 - 3r + 54) = 0
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r = 0 is the only Real Number solution.
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Use the quadratic formula to find the complex solutions.
r = [3 +- sqrt(9 -4*54)]/2
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r = [3 +- sqrt(-207)]/2
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Cheers,
Stan H.