Evaluate
9\left(3m-n\right)^{2}
Expand
81m^{2}-54mn+9n^{2}
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81m^{2}-54mn+9n^{2}
Use binomial theorem \left(a-b\right)^{2}=a^{2}-2ab+b^{2} to expand \left(9m-3n\right)^{2}.
81m^{2}-54mn+9n^{2}
Use binomial theorem \left(a-b\right)^{2}=a^{2}-2ab+b^{2} to expand \left(9m-3n\right)^{2}.
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