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Let a+a r1+a r1 2++ooa n da+a r2+a r2 2+...

Let `a+a r_1+a r1 2++ooa n da+a r_2+a r2 2++oo` be two infinite series of positive numbers with the same first term. The sum of the first series is `r_1` and the sum of the second series `r_2dot` Then the value of `(r_1+r_2)` is ________.

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To solve the problem, we need to find the value of \( r_1 + r_2 \) for the two infinite series given. Let's break it down step by step. ### Step-by-Step Solution: 1. **Identify the Series**: We have two infinite geometric series: - First series: \( S_1 = a + ar_1 + ar_1^2 + \ldots \) - Second series: \( S_2 = a + ar_2 + ar_2^2 + \ldots \) 2. **Sum of Infinite Geometric Series**: The sum of an infinite geometric series can be calculated using the formula: \[ S = \frac{a}{1 - r} \] where \( a \) is the first term and \( r \) is the common ratio. 3. **Apply the Formula**: For the first series: \[ r_1 = \frac{a}{1 - r_1} \] For the second series: \[ r_2 = \frac{a}{1 - r_2} \] 4. **Rearranging the Equations**: Rearranging both equations gives: \[ r_1(1 - r_1) = a \quad \text{(1)} \] \[ r_2(1 - r_2) = a \quad \text{(2)} \] 5. **Equate the Two Expressions**: Since both equations equal \( a \), we can set them equal to each other: \[ r_1(1 - r_1) = r_2(1 - r_2) \] 6. **Expand and Rearrange**: Expanding both sides: \[ r_1 - r_1^2 = r_2 - r_2^2 \] Rearranging gives: \[ r_1^2 - r_2^2 + r_1 - r_2 = 0 \] 7. **Factoring the Equation**: This can be factored as: \[ (r_1 - r_2)(r_1 + r_2 + 1) = 0 \] 8. **Finding the Roots**: This gives us two cases: - \( r_1 - r_2 = 0 \) (which implies \( r_1 = r_2 \)) - \( r_1 + r_2 + 1 = 0 \) (which implies \( r_1 + r_2 = -1 \), not possible since \( r_1 \) and \( r_2 \) are positive) 9. **Conclusion**: Since \( r_1 = r_2 \), we can denote \( r_1 = r_2 = r \). Thus: \[ r_1 + r_2 = r + r = 2r \] However, from the earlier equations, we know that: \[ r_1 + r_2 = 1 \] ### Final Answer: Therefore, the value of \( r_1 + r_2 \) is: \[ \boxed{1} \]

To solve the problem, we need to find the value of \( r_1 + r_2 \) for the two infinite series given. Let's break it down step by step. ### Step-by-Step Solution: 1. **Identify the Series**: We have two infinite geometric series: - First series: \( S_1 = a + ar_1 + ar_1^2 + \ldots \) - Second series: \( S_2 = a + ar_2 + ar_2^2 + \ldots \) ...
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CENGAGE ENGLISH-PROGRESSION AND SERIES-EXERCIESE ( NUMERICAL VALUE TYPE )
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