Find the two middle terms in the expansion of :
For ,
a=3x, and n=9
As n is odd, there are two middle terms i.e.
I. and II.
General term tr+1 is given by,
I. The first middle term is
Therefore, for 5th middle term, r=4
Therefore, the first middle term is
II. The second middle term is
Therefore, for the 6th middle term, r=5
Therefore, the second middle term is
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