\[\boxed{\text{988.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)}\ 5y\left( y^{2} - 3 \right)\left( y^{2} + 3 \right) =\]
\[= 5y\left( y^{4} - 9 \right) = 5y^{5} - 45y\]
\[\textbf{б)} - 8x\left( 4x - x^{3} \right)\left( 4x + x^{3} \right) =\]
\[= - 8x\left( 16x^{2} - x^{6} \right) =\]
\[= 8x^{7} - 128x^{3}\]
\[\textbf{в)}\ \left( a^{4} - 3 \right)\left( a^{4} + 3 \right)\left( a^{8} + 9 \right) =\]
\[= \left( a^{8} - 9 \right)\left( a^{8} + 9 \right) = a^{16} - 81\]
\[\textbf{г)}\ \left( 1 - b^{3} \right)\left( 1 + b^{3} \right)\left( 1 + b^{6} \right) =\]
\[= \left( 1 - b^{6} \right)\left( 1 + b^{6} \right) = 1 - b^{12}\]