Maths-

^{n}C_{r} + ^{2n}C_{r+1} + ^{n}C^{r+2} is equal to (2 r n)

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^{n+1}C_{r+1}
- none of these
- 2 .
^{n}C_{r+2}
^{n+2}C_{r+2}

^{n+1}C_{r+1}^{n}C_{r+2}^{n+2}C_{r+2}#### Answer:The correct answer is: ^{n+2}C_{r+2}

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= Coefficient of x

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=

=

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_{i} 9, i = 1, 2, …6, where 0 < K < 18= Coefficient of x

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^{K}in= Coefficient of x

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