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The number of terms in the expansion of `(x^2+1+1/x^2)^n, n in N` , is:A. number of terms is `2n+1`B. constant term is `2^(n-1)`C. coefficient of `x^(2n-2)` is nD. coefficient of `x^(2)` in n |
Answer» Correct Answer - A::C `(x^(2) + 1 + 1/(x^(2)))` `= .^(n)C_(0)+.^(n)C_(1)(x^(2) + 1/(x^(2)))+.^(n)C_(2)(x^(2) + 1/(x^(2)))^(2)+"......"+.^(n)C_(n)(x^(2)+1/(x^(2)))^(n)` This contains term having `x^(0), x^(2), x^(4), "…….."x^(2n), x^(-2n), x^(-4),"….",x^(-2n)` coefficient of constant term `= .^(n)C_(0) + (.^(n)C_(2))(2) + (.^(n)C_(4)) (.^(4)C_(2)) + (.^(n)C_(6)) (.^(6)C_(3)) + "......" ne 2^(n-1)`. Coefficient of `x^(2n-2)` is `.^(n)C_(n-1) = n` coefficient of `x^(2)` is `.^(n)C_(1) + (.^(n)C_(3))(.^(3)C_(1)) + (.^(n)C_(5))(.^(5)C_(2)) + "....." gt n` |
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