Binomial TheoremHard
Question
If the coefficients of the three successive terms in the binomial expansion of (1 + x)n are in the ratio 1 : 7 : 42, then the first of these terms in the expansion is
Options
A.6th
B.7th
C.8th
D.9th
Solution
nCr-1 : nCr : nCr+1
⇒ 8r = n + 1
⇒ 7r = n − 6
⇒ r = 7
⇒ 8r = n + 1
⇒ 7r = n − 6
⇒ r = 7
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