Find the term independent of x in the expansion of the following: - Maths - Permutations and Combinations

Question

Find the term independent of x in the expansion of the following:

Neha Sethi · Accepted Answer

Dear student
Let r+1th term be independent of x in the given expression
Now, Tr+1=9Cr43x29-r-32xr=9C3439-r-32rx18-3r     
(1)This termm is independent of x, if18-3r=0⇒r=6So, 6+1th ie 7th term is independent of x
 Putting r=6 in (1), we getT7=9C3439-6-326x18-3×6=9!3! 6!433-326=9×8×7×6!3! 6!×642727×278×8=84×27=2268
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