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find the value of given domain and expre...

find the value of given domain and express in form of logarithm function `(1)/(2)-(1)/(2)*(1)/(2^(2))+(1)/(3)*(1)/(2^(3))-…….oo`=

A

`log_(e )((2)/(3))`

B

`log_(e )((3)/(2))`

C

`log_(e )^(2)`

D

`log_(e )^(3)`

Text Solution

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The correct Answer is:
To solve the given series \( S = \frac{1}{2} - \frac{1}{2} \cdot \frac{1}{2^2} + \frac{1}{3} \cdot \frac{1}{2^3} - \ldots \) up to infinity, we can express it in a more manageable form and relate it to a logarithmic function. ### Step-by-Step Solution: 1. **Rewrite the Series**: The series can be rewritten as: \[ S = \sum_{n=1}^{\infty} \frac{(-1)^{n-1}}{n} \cdot \frac{1}{2^n} \] This is a power series where the general term is \( \frac{(-1)^{n-1}}{n} \left( \frac{1}{2} \right)^n \). 2. **Recognize the Series**: This series resembles the Taylor series expansion for \( \log(1+x) \): \[ \log(1+x) = x - \frac{x^2}{2} + \frac{x^3}{3} - \frac{x^4}{4} + \ldots \] Here, we can identify \( x = -\frac{1}{2} \). 3. **Apply the Logarithmic Identity**: Substituting \( x = -\frac{1}{2} \) into the logarithmic series gives: \[ \log(1 - \frac{1}{2}) = -\frac{1}{2} - \frac{(-\frac{1}{2})^2}{2} + \frac{(-\frac{1}{2})^3}{3} - \ldots \] This simplifies to: \[ \log\left(\frac{1}{2}\right) = -\log(2) \] 4. **Relate to the Original Series**: Since our series \( S \) is equal to \( -\log(1 + \frac{1}{2}) \), we have: \[ S = -\log\left(\frac{3}{2}\right) \] Therefore, we can express \( S \) as: \[ S = \log\left(\frac{2}{3}\right) \] 5. **Final Result**: The value of the series is: \[ S = \log\left(\frac{3}{2}\right) \] ### Conclusion: Thus, the value of the given series expressed in the form of a logarithm function is: \[ \log\left(\frac{3}{2}\right) \]
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