\[\boxed{\text{839.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)}\ a(a + 9b)^{2} = a\left( a^{2} + 18ab + 81b^{2} \right) = a³ + 18a²b + 81ab²\]
\[\textbf{б)}\ 6x\left( x^{2} + 5x \right)^{2} = 6x\left( x^{4} + 10x^{3} + 25x^{2} \right) = 6x^{5} + 60x^{4} + 150x³\]
\[\textbf{в)}\ (a + 2)(a - 1)^{2} = (a + 2)\left( a^{2} - 2a + 1 \right) = a³ - 2a^{2} + a + 2a^{2} - 4a + 2 =\]
\[= a³ - 3a + 2\]
\[\textbf{г)}\ (x - 4)(x + 2)^{2} = (x - 4)\left( x^{2} + 4x + 4 \right) =\]
\[= x³ + 4x² + 4x - 4x^{2} - 16x - 16 = x^{3} - 12x - 16\ \]