Evaluate
4\left(b-a\right)\left(2a+b\right)
Expand
4b^{2}+4ab-8a^{2}
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a^{2}+4ab+4b^{2}-9a^{2}
Use binomial theorem \left(p+q\right)^{2}=p^{2}+2pq+q^{2} to expand \left(a+2b\right)^{2}.
-8a^{2}+4ab+4b^{2}
Combine a^{2} and -9a^{2} to get -8a^{2}.
a^{2}+4ab+4b^{2}-9a^{2}
Use binomial theorem \left(p+q\right)^{2}=p^{2}+2pq+q^{2} to expand \left(a+2b\right)^{2}.
-8a^{2}+4ab+4b^{2}
Combine a^{2} and -9a^{2} to get -8a^{2}.
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