Identify the expression for the th term in the expansion of .

MATHEMATICS · Single correct · A Level · Mathematics · Sequences and series · Sequences and series

Problem

Identify the expression for the (r+1)(r+1)th term in the expansion of (a+b)n(a+b)^n. (a) (nr)arbn−r\displaystyle \binom{n}{r} a^{r} b^{n-r} (b) (nr+1)an−rbr+1\displaystyle \binom{n}{r+1} a^{n-r} b^{r+1} (c) (nr)an−rbr\displaystyle \binom{n}{r} a^{n-r} b^{r} (d) (nr−1)an−r+1br−1\displaystyle \binom{n}{r-1} a^{n-r+1} b^{r-1}

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