[JEE Advanced 1994] If the coefficients of the 2nd, 3rd and 4th terms of $(1+x)^n$ are in A.P., then $n=$ ____
If the coefficients of the 2nd, 3rd and 4th terms of $(1+x)^n$ are in A.P., then $n=$ ____
1 Answer
VAVidaara Admin
✓ Vidaara Team
✓ Accepted
· 1mo ago
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Answer: $n=7$.
$2\binom n2=\binom n1+\binom n3\Rightarrow n^2-9n+14=0\Rightarrow n=7$ (rejecting the trivial $n=2$).
JEE Advanced 1994 · Binomial Theorem — verified solution by the Vidaara Team.
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