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The coefficient of x^(n) in the expansio...

The coefficient of `x^(n)` in the expansion of
` log_(e)(1+3x+2x^2)` is

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To find the coefficient of \( x^n \) in the expansion of \( \log_e(1 + 3x + 2x^2) \), we can follow these steps: ### Step 1: Rewrite the logarithmic expression We start with the expression \( \log_e(1 + 3x + 2x^2) \). We can factor the quadratic expression inside the logarithm: \[ 1 + 3x + 2x^2 = (1 + x)(1 + 2x) \] ### Step 2: Use logarithmic properties Using the property of logarithms that states \( \log(mn) = \log(m) + \log(n) \), we can rewrite the expression as: \[ \log_e(1 + 3x + 2x^2) = \log_e(1 + x) + \log_e(1 + 2x) \] ### Step 3: Expand each logarithmic term Next, we can use the Taylor series expansion for \( \log(1 + u) \), which is given by: \[ \log(1 + u) = \sum_{k=1}^{\infty} \frac{(-1)^{k-1} u^k}{k} \] Applying this to both terms: 1. For \( \log_e(1 + x) \): \[ \log_e(1 + x) = \sum_{k=1}^{\infty} \frac{(-1)^{k-1} x^k}{k} \] 2. For \( \log_e(1 + 2x) \): \[ \log_e(1 + 2x) = \sum_{m=1}^{\infty} \frac{(-1)^{m-1} (2x)^m}{m} = \sum_{m=1}^{\infty} \frac{(-1)^{m-1} 2^m x^m}{m} \] ### Step 4: Combine the expansions Now we can combine the two series: \[ \log_e(1 + 3x + 2x^2) = \sum_{k=1}^{\infty} \frac{(-1)^{k-1} x^k}{k} + \sum_{m=1}^{\infty} \frac{(-1)^{m-1} 2^m x^m}{m} \] ### Step 5: Find the coefficient of \( x^n \) To find the coefficient of \( x^n \), we need to look at the contributions from both series: - From \( \log_e(1 + x) \), the coefficient of \( x^n \) is \( \frac{(-1)^{n-1}}{n} \). - From \( \log_e(1 + 2x) \), the coefficient of \( x^n \) is \( \frac{(-1)^{n-1} 2^n}{n} \). Thus, the total coefficient of \( x^n \) in the expansion is: \[ \text{Coefficient of } x^n = \frac{(-1)^{n-1}}{n} + \frac{(-1)^{n-1} 2^n}{n} = \frac{(-1)^{n-1}(1 + 2^n)}{n} \] ### Final Answer The coefficient of \( x^n \) in the expansion of \( \log_e(1 + 3x + 2x^2) \) is: \[ \frac{(-1)^{n-1}(1 + 2^n)}{n} \]
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OBJECTIVE RD SHARMA ENGLISH-EXPONENTIAL AND LOGARITHMIC SERIES-Chapter Test
  1. The series expansion of log{(1+x)^(1+x)(1-x)^(1-x)} is

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  2. 2log x-log(x+1)-log(x-1) is equals to

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  3. The coefficient of x^(n) in the expansion of log(e)(1+3x+2x^2) is

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  4. If x ne 0 then the sum of the series 1+(x)/(2!)+(2x^(2))/(3!)+(3x^(3...

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  5. If log(1-x+x^(2))=a(1)x+a(2)x^(2)+a(3)x^(3)+…and n is not a mutiple of...

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  6. If log(1-x+x^(2))=a(1)x+a(2)x^(2)+a(3)x^(3)+… then a(3)+a(6)+a(9)+.....

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  7. The coefficient of x^(n) in the expansion of log(a)(1+x) is

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  8. The coeffiecent of n^(-r) in the expansion of log(10)((n)/(n-1)) is

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  9. The sum of the series (x-1)/(x+1)+1/2(x^(2)-1)/(x+1)^(2)+1/3(x^(3)-1...

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  10. The sum of series 2[ 7^(-1)+3^(-1).7^(-3)+5^(-1).7^(-5)+...] is

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  11. The coefficient of x^(6) in the expansion of log{(1+x)^(1+x)(1-x)^(...

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  12. The sum of the series 1/2x^2+2/3x^3+3/4x^4+4/5x^5+... is :

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  13. If x,y,z are three consecutive positive integers and X-Z + 2 = 0, then...

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  14. The sum of the series ((1)^(2).2)/(1!)+(2^(2).3)/(2!)+(3^(2).4)/(3!)+(...

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  15. The value of 1-log(e)2+(log(e)2)^(2)/(2!)-(log(e)2)^(3)/(3!)+.. is

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  16. 1+(loge n)^2 /(2!) + (loge n )^4 / (4!)+...=

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  17. (2)/(3!)+(4)/(5!)+(6)/(7!)+..is equal to

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  18. Sum of n terms of the series 1/(1.2.3.4.)+1/(2.3.4.5) +1/(3.4.5.6)+.....

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  19. The value of 1+(log(e)x)+(log(e)x)^(2)/(2!)+(log(e)x)^(3)/(3!)+…inft...

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  20. If |x|lt1 then the coefficient of x^(3) in the expansion of log(1+x+x^...

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