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The coefficient of `x^(n)` in the exansion of `log_(e)(1+3x+2x^(2))` isA. `(-1)^(n)((2^(n)+1)/(n))`B. `((-1)^(n+1))/(n)(2^(n)+1)`C. `(2^(n+1))/(n)`D. none of these |
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Answer» Answer: We have `log(1+3x+2x^(2))` `=log(1+x)+log(1+2x)` `=underset(n=1)overset(infty)Sigma(-1)^(n-1)(x^(n))/(n)+underset(n=1)overset(infty)Sigma(-1)^(n-1)(2x)^(n)/(n)` ltbgt `=underset(n=1)overset(infty)Sigma(-1)^(n-1)((1)/(n)+(2^(n))/(n))x^(n)` `therefore "coefficeient of" x^(n)=(-1)^(n-1)((2^(n)+1)/(n))=(-1)^(n+1)(2^(n)+1)/(n))` |
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