The middle term in the expression of ( x - 1 x )^ 18 is - Vidyadip

MCQ

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

A
$^{18}{C_9}$
✓
${ - ^{18}}{C_9}$
C
$^{18}{C_0}$
D
${ - ^{18}}{C_{10}}$

✓

Answer

Correct option: B.

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

b
(b) If $n$ is even.

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

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

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