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Write M ∑ R = 0 N + R C R in the Simplified Form.

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प्रश्न

Write \[\sum^m_{r = 0} \ ^{n + r}{}{C}_r\] in the simplified form.

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उत्तर

We know:

\[\ ^{n}{}{C}_r + \ ^{n}{}{C}_{r - 1} = \ ^ {n + 1}{}{C}_r\]
\[\sum^m_{r = 0} \ ^{n + r}{}{C}_r = \ ^{n}{}{C}_0 + \ ^{n + 1}{}{C}_1 + \ ^{n + 2}{}{C}_2 + \ ^{n + 3}{}{C}_3 + . . . + \ ^{n + m}{}{C}_m \]
\[ \because \ ^{n}{}{C}_0 = \ ^{n + 1}{}{C}_0 \]
\[ \therefore \sum^m_{r = 0} \ ^{n + r}{}{C}_r = \ ^{n + 1}{}{C}_0 + \ ^{n + 1}{}{C}_1 + \ ^{n + 2}{}{C}_2 + \ ^{n + 3}{}{C}_3 + . . . + \ ^{n + m}{}{C}_m \]
\[Using \ ^{n}{}{C}_{r - 1} + \ ^{n}{}{C}_r = \ ^{n + 1}{}{C}_r : \]
\[ \Rightarrow \sum^m_{r = 0} \ ^{n + r}{}{C}_r = \ ^{n + 2}{}{C}_1 + \ ^{n + 2}{}{C}_2 + \ ^{n + 3}{}{C}_3 + . . . + \ ^{n + m}{}{C}_m \]
\[ \Rightarrow \sum^m_{r = 0} \ ^{n + r}{}{C}_r = \ ^{n + 3}{}{C}_2 + \ ^ {n + 3}{}{C}_3 + . . . + \ ^{n + m}{}{C}_m\]
Proceeding in the same way:
\[\sum^m_{r = 0} \ ^{n + r}{}{C}_r = \ ^{n + m}{}{C}_{m - 1} + \ ^ {n + m}{}{C}_m = \ ^{n + m + 1}{}{C}_m \]
\[ \Rightarrow \sum^m_{r = 0} \ ^{n + r}{}{C}_r = \ ^{n + m + 1}{}{C}_m\]
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अध्याय 17: Combinations - Exercise 17.4 [पृष्ठ २४]

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आर.डी. शर्मा Mathematics [English] Class 11
अध्याय 17 Combinations
Exercise 17.4 | Q 1 | पृष्ठ २४

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