\[\boxed{\text{944.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)}\ (y - 3)\left( y^{2} + 9 \right)(y + 3) -\]
\[- \left( 2y^{2} - y \right)^{2} - 19 =\]
\[= \left( y^{2} - 9 \right)\left( y^{2} + 9 \right) -\]
\[- \left( 4y^{4} - 4y^{3} + y^{2} \right) - 19 =\]
\[= y^{4} - 81 - 4y^{4} + 4y^{3} - y^{2} -\]
\[- 19 = - 3y^{4} + 4y^{3} - y^{2} - 100\]
\[\textbf{б)}\ (1 - a)\left( 1 - a^{2} \right) +\]
\[+ (1 + a)\left( 1 + a^{2} \right) -\]
\[- 2a(1 + a)(a - 1) =\]
\[= \left( 1 - a^{2} - a + a^{3} \right) + 1 + a^{2} +\]
\[+ a + a^{3} - 2a\left( a^{2} - 1 \right) =\]
\[= 1 - a^{2} - a + a^{3} + 1 + a^{2} +\]
\[+ a + a^{3} - 2a^{3} + 2a = 2 + 2a\]