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The number of real negative terms in the...

The number of real negative terms in the binomial expansion of `(1+i x)^(4n-2),n in N ,x >0` is

A

n

B

n+1

C

n-1

D

2n

Text Solution

Verified by Experts

The correct Answer is:
A
`T_(r+1) = .^(4n-2)C_(r)("ix")^(r )`
`T_(r+1)` is negative, if `i^(r)` is negative and real.
`i^(r ) = - 1`
`rArr r = 2, 6, 10,"……"` which form an `A.P.`
`0 le r le 4n - 2`
`4n - 2 = 2 + (r-1)4`
`rArr r = n`
The required number of terms is n.
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CENGAGE-BINOMIAL THEOREM-Exercise (Single)
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