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18Find the 13th term in the expansion of (9x - 1/3√x)18 |
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Answer» =18564 Step-by-step explanation: It is known that(R+1) term (T r+1 ) in the binomial expansion of (a+b) n is given by T r+1 = n C r a n−r b r
THUS 13 th term in the expansion of (9x− 3 x
1 ) 18 is T 13 =T 12+1 = 18 C 12 (9x) 18−12 (− 3 x
1 ) 12
=(−1) 12
12!6! 18! (9) 6 (x) 6 ( 3 1 ) 12 ( x
1 ) 12
= 12!.6.5.4.3.2 18.17.16.15.14.13.12! .x 6 ( x 6
1 ).3 12 ( 3 12
1 ) =18564 |
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