Middle term in expression of {left( {x - frac{1}{x}} right)^{18}} is

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7.Binomial Theorem

easy

The middle term in the expression of ${\left( {x - \frac{1}{x}} \right)^{18}}$ is

A

$^{18}{C_9}$

B

${ - ^{18}}{C_9}$

C

$^{18}{C_0}$

D

${ - ^{18}}{C_{10}}$

Solution

(b) If $n$ is even.

$\therefore $Middle term is $10^{th}$ term.

==> ${T_{10}} = {}^{18}{C_9}{(x)^9}.\,{\left( { – \frac{1}{x}} \right)^9} = {\rm{ }} – {}^{18}{C_9}$.

Standard 11

Mathematics

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