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0 votes
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in Mathematics by (71.2k points)

Co efficient of middle term in expansion of (x - x3/5)8 = .........

(a) 14/625

(b) 70/625

(c) 14/125

(d) 70/125

1 Answer

+1 vote
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Best answer

Correct option: (b) 70/625

Explanation:

n = 8 ⇒ middle term is (n/2) + 1 = 5th term

∵  Tr+1 = ncr an–rbr hence

T5 = 8c4 (x)8–4 [(– x3) / 5]4 

= 8c4 (x)4 (x12 / 54)

= (8c4 / 54) x16 

T5 = [(70) / (625)]x16 i.e. coefficient is [(70) / (625)]

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