Expand
49x^{2}+14xy+y^{2}-81
Evaluate
\left(7x+y\right)^{2}-81
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49x^{2}+14xy+y^{2}-81
Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(7x+y\right)^{2}.
49x^{2}+14xy+y^{2}-81
Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(7x+y\right)^{2}.
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