Question

кто поможет, даю 50 балов​

Answer 1

$\displaystyle\bf\\1)\\\\15a\cdot\frac{a+4}{3} +12a^{2} \cdot \frac{5-2a}{6}=5a\cdot(a+4)+2a^{2} \cdot(5-2a)=\\\\\\=5a^{2} +20a+10a^{2} -4a^{3} =-4a^{3} +15a^{2} +20a\\\\\\2)\\\\24c^{3} \cdot\frac{c^{2} +2c-3}{8} -18c^{2} \cdot\frac{c^{3} -c^{2} +2}{9} =\\\\\\=3c^{3} \cdot(c^{2} +2c-3)-2c^{2}\cdot(c^{3} -c^{2}+2)=\\\\\\=3c^{5} +6c^{4} -9c^{3} -2c^{5} +2c^{4} -4c^{2} =c^{5} +8c^{4}-9c^{3} -4c^{2} \\\\\\3)\\\\34x\cdot\frac{x-y}{17} -45y\cdot\frac{x-2y}{15} -y(6y-5x)=$

$\displaystyle\bf\\=2x\cdot(x-y)-3y\cdot(x-2y)-6y^{2} +5xy=\\\\\\=2x^{2} -2xy-3xy+6y^{2} -6y^{2}+5xy=2x^{2}$