- A
- B
- C
- D
View written solutionFree
Correct answer: B, C
Step-by-step Derivations:
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Analyze the Limit Expression
Let the given limit be . The expression inside the limit is: We need to find the set of all pairs for which .
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Use Asymptotic Equivalents for
For large values of , we can use the following standard limits and approximations:
- As , . Therefore, . This is because .
- As , . Since , we have . More formally, .
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Simplify the Expression
Based on these equivalents, the behavior of for large is similar to the behavior of the following expression: Simplifying : The limit of is 0 if and only if the limit of is 0, because .
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Determine the Conditions for the Limit to be Zero
We need to find when . The term is a bounded function that oscillates between -1 and 1. For the overall limit to be zero, the magnitude of the other part must tend to zero. This is a direct application of the Squeeze Theorem. So, the condition is: We analyze this limit based on the power of in the denominator, which is .
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Case 1: In this case, the power of in the denominator is positive. Since polynomial functions grow faster than logarithmic functions, the limit will be 0, regardless of the value of the exponent . So, if , then .
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Case 2: Let where . The expression becomes . This limit is , not 0. So these pairs are not in .
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Case 3: The expression becomes . For this limit to be 0, the exponent must be negative. So, we need . If , the limit is or 1, and the original limit would not be 0 (it would not exist).
Summary of Conditions: A pair is in the set if and only if: (i) OR (ii) AND .
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Evaluate Each Option
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A: . Since , condition (i) is not met. Condition (ii) is also not met. Thus, .
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B: . Since , condition (i) is met. Thus, .
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C: . Since , condition (i) is met. Thus, .
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D: . Condition (i) is not met. We check condition (ii). We have . Now check the second part of condition (ii): . Since is not less than 0, the condition is not met. Thus, .
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Conclusion:
The pairs that belong to the set are and . Therefore, options B and C are correct.
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