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Question
Find the value of `""^15"C"_4 + ""^15"C"_5`
Solution
`""^15"C"_4 + ""^15"C"_5`
= `""^15"C"_5 + ""^15"C"_4`
= `""^15"C"_5 + ""^15"C"_(5-1)`
= `""^16"C"_5` .......`[∵ ""^"n""C"_"r" + ""^"n""C"_"r - 1" = ""^("n" + 1)"C"_"r"]`
= 4368
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