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In the expansion of (1+x)^n , 7th and 8t...

In the expansion of `(1+x)^n ,` 7th and 8th terms are equal. Find the value of `(` 7/x ` +6)^2` .

Text Solution

Verified by Experts

The correct Answer is:
`n^(2)`
Since the `7^(th)` and `8^(th)` terms are equal , we have
`.^(n)C_(6)x^(6) =.^(n)C_(7)x^(7)`
or `x=(.^(n)C_(6))/(.^(n)C_(7))=(7)/(n-6)`
or `(7/x+6)=n^(2)`
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  • If in the expansion of (1+x)^(n) the coefficient of 2nd, 3rd and 4th terms are in A.P., then the value of n is-

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    B
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