If the ratio of the seventh term from the beginning of the binomial expansion of (21/3+131/3)x to the seventh term from the end is 16, then the value of x is
A
7
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B
5
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C
11
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D
9
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Solution
The correct option is D9 Seventh term from the beginning =xC6(21/3)x−6(3−1/3)6 Seventh term from the last =xCx−6(21/3)6(3−1/3)x−6 We know that, xC6(21/3)x−6(3−1/3)6xCx−6(21/3)6(3−1/3)x−6=16 ⇒x=9