\[\boxed{\text{947.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)} - 20x^{4}y^{2} - 35x^{3}y^{3} =\]
\[= - 5x³y²(4x + 7y)\]
\[\textbf{б)}\ 3a³b²c + 9ab²c³ =\]
\[= 3ab²c(a^{2} + 3c^{2})\]
\[\textbf{в)} - 1,2a^{3}b + 1,2b^{4} =\]
\[= 1,2b\left( - a^{3} + b^{3} \right) =\]
\[= 1,2b(b - a)(b^{2} + ab + a^{2})\]
\[\textbf{г)}\ 7,2x^{4}y^{4} - 1,8x^{4}y^{2} =\]
\[= 1,8x^{4}y^{2}\left( 4y^{2} - 1 \right) =\]
\[= 1,8x^{4}y^{2}(2y - 1)(2y + 1)\]