Limits of sequences - supremum and infimum, topology of R, Heine–Borel theorem, Bolzano–Weierstrass theorem, compactness equivalence to closed and bounded - One Line Questions
1.
Which of the following is an example of a closed set in R? —
[0, 1]
2.
Which of the following is an example of an open set in R? —
(0, 1)
3.
Consider the set S = {1/n | n is a positive integer}. What is the supremum of S? —
1
4.
Consider the set S = {1/n | n is a positive integer}. What is the infimum of S? —
0
5.
If a sequence {a_n} is bounded, it does NOT necessarily have: —
A monotonic subsequence
6.
If a subset of R is infinite and bounded, the Bolzano–Weierstrass theorem guarantees the existence of: —
A convergent subsequence
7.
What is a limit point (or accumulation point) of a set S? —
A point such that every open interval containing it also contains a point of S different from the point itself.
8.
What is the definition of a convergent sequence in real analysis? —
A sequence whose terms get arbitrarily close to a specific real number as the index increases.
9.
In the topology of R, what is an open set? —
A set that is a union of open intervals.
10.
A set S in R is closed if and only if it contains: —
All its limit points.
11.
The Bolzano–Weierstrass theorem is a direct consequence of the: —
Completeness Property of R
12.
Which property is equivalent to compactness for a subset of R? —
Being closed and bounded
13.
Which theorem establishes an equivalence between compactness and being closed and bounded for subsets of R? —
Heine–Borel Theorem
14.
Which property of real numbers is crucial for the existence of limits of sequences? —
Completeness property
15.
The Bolzano–Weierstrass theorem is also known as the: —
Boundedness Theorem
16.
The statement 'Every infinite bounded subset of R has a limit point' is the essence of which theorem? —
Bolzano–Weierstrass Theorem
17.
Which of the following is a correct statement about the supremum (sup) and infimum (inf) of a non-empty set S of real numbers? —
If S is bounded above, sup S is the smallest real number that is greater than or equal to every element of S.
18.
The Bolzano–Weierstrass theorem is crucial for proving that a continuous function on a compact set attains its: —
Maximum and minimum values
19.
Consider the set of all rational numbers in the interval [0, 1]. This set is infinite and bounded. What does Bolzano–Weierstrass imply? —
It has a limit point within [0, 1].
20.
What does it mean for a set to be compact in the context of real analysis? —
It must be bounded and contain all its limit points.
21.
If a set K in R is compact, what can be said about any sequence {x_n} in K? —
It has a subsequence that converges to a point in K.
22.
According to the Heine–Borel theorem, what is a necessary and sufficient condition for a subset of R to be compact? —
It must be closed and bounded.
23.
If a sequence {a_n} converges to L, what can be said about its boundedness? —
It must be bounded.
24.
The property that any sequence in a compact set K has a subsequence converging to a point in K is equivalent to: —
K being closed and bounded
25.
If a sequence {a_n} converges to L, which of the following must be true? —
For every epsilon > 0, there exists N such that |a_n - L| < epsilon for all n >= N.
26.
The Bolzano–Weierstrass theorem can be used to prove that every convergent sequence has a: —
Limit point
27.
Consider the interval [0, 1]. Is it compact according to the Heine–Borel theorem? —
Yes, because it is closed and bounded.
28.
If a set of real numbers is bounded above, does it necessarily have a supremum? —
Yes, by the completeness property of real numbers.
29.
If a set S is closed and bounded, then S is: —
Compact
30.
The Heine–Borel theorem implies that a closed and bounded interval [a, b] in R is: —
Compact
31.
If a set K is compact in R, then K is necessarily: —
Bounded
32.
If a set S is compact, it implies that S is: —
Sequentially compact
33.
The Heine–Borel theorem states that a subset of R is compact if and only if it is: —
Closed and bounded
34.
The definition of compactness using open covers is also known as: —
Heine–Borel Property
35.
The Bolzano–Weierstrass theorem is a key result for proving the existence of: —
Limit points
36.
If a sequence {a_n} has a limit L, then L is a: —
Limit point of the set {a_n | n in N}
37.
What is a closed set in the topology of R? —
The complement of an open set.
38.
What is the Heine–Borel theorem primarily concerned with? —
The property of compactness for subsets of R.
39.
What does the topology of R refer to? —
The study of open sets, closed sets, and their properties on the real line.
40.
Which of the following is NOT a property of closed sets in R? —
The intersection of any collection of closed sets is closed.
41.
Let S be a non-empty set of real numbers bounded above. The supremum of S is: —
The smallest number that is greater than or equal to all elements of S.
42.
Let S be a non-empty set of real numbers bounded below. The infimum of S is: —
The largest number that is less than or equal to all elements of S.
43.
What is the supremum of a set of real numbers? —
The least upper bound of the set.
44.
What is the infimum of a set of real numbers? —
The greatest lower bound of the set.
45.
Which of the following is NOT a property of open sets in R? —
The union of any collection of open sets is open.
46.
What is the relationship between the set of limit points of a set S and the closure of S? —
The set of limit points is a subset of the closure.
47.
What is the relationship between the Bolzano–Weierstrass theorem and the Heine–Borel theorem? —
Heine–Borel is a consequence of Bolzano–Weierstrass and the definition of open sets.
48.
What does the Bolzano–Weierstrass theorem state about bounded infinite subsets of R? —
They must have at least one limit point.
49.
Consider the open interval (0, 1). Is it compact according to the Heine–Borel theorem? —
No, because it is not closed.
50.
Consider the set of integers Z. Is it compact? —
No, it is not bounded.