binomial theorem-0-
2009-10-26 10:53 pm
It is given that n is a positive integer, and the 7th term in the expansion of [2(x^2) + 1/(2x)]^n in descending powers of x is the constant term. Find the value of n and the 7th term.
回答 (1)
2009-10-26 11:41 pm
✔ 最佳答案
The general term = nCr (2x^2)(n - r) (1/2x)^r= (2)^(n - 2r) nCr x^(2n - 3r)
For the 7th term, r = 6, it is a constant term
So, 2n - 3(6) = 0
n = 9
The 7th term
= (2)^(9 - 12) 9C7
= 9/2
參考: Physics king
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