Math Problem Statement

If 𝐸={1βˆ’βˆ‘π‘›π‘š=114π‘š:π‘›βˆˆπ‘}, then which of the following is true

a. π‘€π‘Žπ‘₯.𝐸=1, 𝑆𝑒𝑝.𝐸=1, 𝑀𝑖𝑛.𝐸=23, 𝐼𝑛𝑓.𝐸=23

b. π‘€π‘Žπ‘₯.𝐸=34, 𝑆𝑒𝑝.𝐸=34, 𝑀𝑖𝑛.𝐸=23, 𝐼𝑛𝑓.𝐸= does not exist

c. π‘€π‘Žπ‘₯.𝐸=34, 𝑆𝑒𝑝.𝐸=34, 𝑀𝑖𝑛.𝐸= does not exist , 𝐼𝑛𝑓.𝐸=does not exist

d. π‘€π‘Žπ‘₯.𝐸=34, 𝑆𝑒𝑝.𝐸=34, 𝑀𝑖𝑛.𝐸= does not exist , 𝐼𝑛𝑓.𝐸=23

Solution

Let's analyze the given set and identify the values of the maximum, supremum, minimum, and infimum.

Given Set Definition:

The set EE is defined as:

E={1βˆ’βˆ‘m=114mn:n∈N}E = \left\{ 1 - \sum_{m=1}^{14} \frac{m}{n} : n \in \mathbb{N} \right\}

Breaking Down the Expression:

  1. Summation: βˆ‘m=114mn\sum_{m=1}^{14} \frac{m}{n} is a summation of a series from m=1m = 1 to m=14m = 14. This equals:

βˆ‘m=114mn=1+2+3+…+14n=14β‹…152n=105n\sum_{m=1}^{14} \frac{m}{n} = \frac{1 + 2 + 3 + \ldots + 14}{n} = \frac{\frac{14 \cdot 15}{2}}{n} = \frac{105}{n}

  1. Set EE: Each element in the set is of the form:

1βˆ’105n1 - \frac{105}{n}

where n∈Nn \in \mathbb{N}. As nn takes different values, EE will vary based on nn.

Evaluating EE:

  • As nn becomes larger, 105n\frac{105}{n} approaches 0, making 1βˆ’105n1 - \frac{105}{n} approach 1.
  • For n=1n = 1, 1βˆ’1051=1βˆ’105=βˆ’1041 - \frac{105}{1} = 1 - 105 = -104.
  • For n=2n = 2, 1βˆ’1052=1βˆ’52.5=βˆ’51.51 - \frac{105}{2} = 1 - 52.5 = -51.5.
  • As nn increases, the values approach 1 from the left.

Analyzing Extremes:

  1. Supremum (sup⁑E\sup E) is the least upper bound of the set. Here, the supremum is 1.
  2. Maximum (max⁑E\max E) is the greatest element in the set, if it exists. As nn becomes large, 1βˆ’105nβ‰ˆ11 - \frac{105}{n} \approx 1, but 1 is not achieved for any finite nn. Hence, max⁑E\max E does not exist.
  3. Infimum (inf⁑E\inf E) is the greatest lower bound. Since n=1n = 1 gives βˆ’104-104, which is the smallest value, the infimum is βˆ’104-104.
  4. Minimum (min⁑E\min E) is the least element in the set. It exists and is βˆ’104-104 when n=1n = 1.

Conclusion:

Let's match this with the provided options:

  • Option A: max⁑E=1,sup⁑E=1,min⁑E=23,inf⁑E=23\max E = 1, \sup E = 1, \min E = 23, \inf E = 23. This is incorrect.
  • Option B: max⁑E=34,sup⁑E=34,min⁑E=23,inf⁑E\max E = \frac{3}{4}, \sup E = \frac{3}{4}, \min E = \frac{2}{3}, \inf E does not exist. This is incorrect.
  • Option C: (\max E = \frac{3}{4}, \sup E

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Math Problem Analysis

Mathematical Concepts

Set Theory
Series and Summation
Real Analysis

Formulas

Sum of integers from 1 to 14: βˆ‘_{m=1}^{14} m = 105
Expression for E: 1 - 105/n

Theorems

Supremum and Infimum of a set
Upper and Lower Bound Theorems

Suitable Grade Level

Undergraduate