Question

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Answer 1

$1)\; \; (a^2+3ab+b^2)(7a-5b)=7a^3-5a^2b+21a^2b-15ab^2+7ab^2-5b^3=\\\\=7a^3+16a^2b-8ab^2-5b^3\\\\\\2)\; \; (\frac{1}{3}a^2b-\frac{3}{5}ab^2)(15a-30b)=5a^3b-10a^2b^2-9a^2b^2+18ab^3=\\\\=5a^3b-19a^2b^2+18ab^3$