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giovkast

  • 3 years ago

determine the coefficient of x^5 in the expression (2x-3)^8 help pls!!

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  1. mukushla
    • 3 years ago
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    going with binomial theorem\[(a+b)^n=\sum_{k=0}^{n} \binom{n}{k} a^k b^{n-k}\]and setting a=2x ,b=-3 and n=8 ... will be your start point

  2. giovkast
    • 3 years ago
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    \[\sum_{k=0}^{8} \left(\begin{matrix}8 \\ 5\end{matrix}\right) 2^5 (-3) ^3 x^5\] Is this is?

  3. mukushla
    • 3 years ago
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    u just need to evaluate one term of the sum and its where k equals to 5 so just \[ \left(\begin{matrix}8 \\ 5\end{matrix}\right) 2^5 (-3) ^3 x^5\]

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