If ^nC_r + ^nC_{r+1} = ^{n+1}C_x, then x = ?

Permutations Practice Test 2

Question : 3 of 30

Marks: +1, -0

^nC_r + ^nC_{r+1} = ^{n+1}C_x

, then

x = ?

Solution:

^{n + 1}C_x = ^nC_r +^nC_{r + 1} = ^{n + 1}C_{r + 1}

⇒ x = r + 1

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