Khai triển (3x+1)10 cho tới x3.
\(\begin{array}{*{20}{l}}
\begin{array}{l}
{\left( {3x + 1} \right)^{10}} = \sum\limits_{k = 0}^{10} {C_{10}^k} {\left( {3x} \right)^k}\\
= 1 + C_{10}^1\left( {3x} \right) + C_{10}^2{\left( {3x} \right)^2} + C_{10}^3{\left( {3x} \right)^3} + ...
\end{array}\\
{ = 1 + 30x + 405{x^2} + 3240{x^3} + ....}
\end{array}\)
-- Mod Toán 11
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