Question
If the ratio of the coefficient of third and fourth term in the expansion of (x−12x)n is 1:2, then the value of n will be
Answer: Option D
:
D
T3 =nC2(x)n−2(−12x)2 andT4 =nC3(x)n−3(−12x)3
But according to the condition,
−n(n−1)×3×2×1×8n(n−1)(n−2)×2×1×4 = 12 ⇒n = -10
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:
D
T3 =nC2(x)n−2(−12x)2 andT4 =nC3(x)n−3(−12x)3
But according to the condition,
−n(n−1)×3×2×1×8n(n−1)(n−2)×2×1×4 = 12 ⇒n = -10
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