\[\boxed{\text{951.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)}\ y³ - y^{5} = y^{3}\left( 1 - y^{2} \right) =\]
\[= y^{3}(1 - y)(1 + y)\]
\[\textbf{б)}\ 2x - 2x^{3} = 2x\left( 1 - x^{2} \right) =\]
\[= 2x(1 - x)(1 + x)\]
\[\textbf{в)}\ 81x² - x^{4} = x^{2}\left( 81 - x^{2} \right) =\]
\[= x²(9 - x)(9 + x)\]
\[\textbf{г)}\ 4y³ - 100y^{5} =\]
\[= 4y^{3}\left( 1 - 25y^{2} \right) =\]
\[= 4y³(1 - 5y)(1 + 5y)\]