\[\boxed{\text{904\ (904).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ (a + 2b)(a - 2b)\left( a^{2} + 4b^{2} \right) =\]
\[= a^{4} - 16b^{4}\]
\[(a + 2b)(a - 2b)\left( a^{2} + 4b^{2} \right) =\]
\[= a^{4} - 16b^{4}\]
\[\left( a^{2} - 4b^{2} \right)\left( a^{2} + 4b^{2} \right) =\]
\[= a^{4} - 16b^{4}\]
\[a^{4} - 16b^{4} = a^{4} - 16b^{4} \Longrightarrow ч.т.д.\]
\[\textbf{б)}\ (x - 1)(x + 1)\left( x^{2} + 1 \right)\left( x^{4} + 1 \right) =\]
\[= x^{8} - 1\]
\[(x - 1)(x + 1)\left( x^{2} + 1 \right)\left( x^{4} + 1 \right) =\]
\[= x^{8} - 1\]
\[\left( x^{2} - 1 \right)\left( x^{2} + 1 \right)\left( x^{4} + 1 \right) =\]
\[= x^{8} - 1\]
\[\left( x^{4} - 1 \right)\left( x^{4} + 1 \right) = x^{8} - 1\]
\[x^{8} - 1 = x^{8} - 1 \Longrightarrow ч.т.д.\]
\[\left( a^{3} - 8 \right)\left( a^{3} + 8 \right) = a^{6} - 64\]
\[a^{6} - 64 = a^{6} - 64 \Longrightarrow ч.т.д.\]
\[\textbf{г)}\ \left( c^{2} - c - 2 \right)\left( c^{2} + c - 2 \right) =\]
\[= c^{4} - 5c^{2} + 4\]
\[\left( c^{2} - c - 2 \right)\left( c^{2} + c - 2 \right) =\]
\[= c^{4} - 5c^{2} + 4\]
\[\left( \left( c^{2} - 2 \right) - c \right)\left( \left( c^{2} - 2 \right) + c \right) =\]
\[= c^{4} - 5c^{2} + 4\]
\[\left( c^{2} - 2 \right)^{2} - c^{2} =\]
\[= c^{4} - 4c^{2} + 4 - c^{2} =\]
\[= c^{4} - 5c^{2} + 4\]
\[c^{4} - 5c^{2} + 4 =\]
\[= c^{4} - 5c^{2} + 4 \Longrightarrow ч.т.д.\]