Số hạng tổng quát:
$\begin{array}{l} {T_{k + 1}} = C_8^k{.1^{8 - k}}.{\left( {{x^4} + {x^6}} \right)^k}\\ {T_{k + 1}} = C_8^k.C_k^p.{\left( {{x^4}} \right)^{k - p}}.{\left( {{x^6}} \right)^p}\left( {0 \le p < k \le 8} \right)\\ {T_{k + 1}} = C_8^k.C_k^p.{x^{4k - 4p}}.{x^{6p}}\\ {T_{k + 1}} = C_8^k.C_k^p.{x^{4k + 2p}}\\ \Rightarrow {x^{4k + 2p}} = {x^{16}}\\ \Rightarrow 4k + 2p = 16 \Rightarrow 2k + p = 8\\ + k = 3,p = 2 \Rightarrow C_8^3.C_3^2\\ + k = 4,p = 0 \Rightarrow C_8^4.C_8^0 = C_8^4 \end{array}$
