Function Set Sequences
1. Problem 16 concerns the behavior of the function images of set operations.
2. Statement I: $f(A \cup B) = f(A) \cup f(B)$
- This is always true for functions because the image of the union is the union of the images.
3. Statement II: $f(A \cap B) = f(A) \cap f(B)$
- Generally false. The image of an intersection is a subset of the intersection of images, but equality need not hold because different elements in $A \cap B$ may map to the same point.
4. Statement III: Given $C \subseteq B$, then $f(C) \subseteq f(B)$
- True because if every element of $C$ is in $B$, their images under $f$ must lie within $f(B)$.
5. Conclusion for 16: Only statements I and III must be true. So the answer is (D) I and III only.
6. Problem 17 asks which statement about sequences is FALSE.
7. Option (A): Every unbounded sequence is divergent.
- True by definition, since boundedness is necessary for convergence.
8. Option (B): Every bounded sequence is convergent.
- False. Bounded sequences may fail to converge (example: $a_n = (-1)^n$).
9. Option (C): If $\lim_{n \to \infty} a_n = a$ and $f$ is continuous at $a$, then $\lim_{n \to \infty} f(a_n) = f(a)$.
- True by continuity of $f$.
10. Option (D): The Cauchy criterion interpretation for convergent sequences.
- True.
11. Option (E): The equivalence of $\lim_{n \to \infty} a_n = a$ and $\lim_{n \to \infty} |a_n - a| = 0$.
- True.
12. Conclusion for 17: The false statement is (B).
13. Problem 18 concerns analyzing $g$ from its derivative graph $g'$:
14. Analysis of statement I: Local max at $x=0$ and min at $x=4$.
- At $x=0$, we do not have derivative info but $g'(x)$ starts high at 2 at $x=1$ and decreases to $x=3$.
- Local maximum requires $g'$ changes from positive to negative.
- At $x=4$, $g'$ is $-1$, and goes negative before and after, not consistent with local min.
15. Analysis of statement II: Local max at $x=2$ and local min at $x=5$.
- From $x=1$ to 3, $g'$ decreases from 2 to -2.
- So at $x=2$, $g'$ passes positive to negative suggests a local max.
- At $x=5$, $g'$ at -3 shifts to increase up to 1 at $x=7$, so passes negative to positive, indicating local min.
16. Analysis of statement III: $g(2) = g(5)$.
- Since $g'$ is derivative, integral of $g'$ from 2 to 5 gives $g(5) - g(2)$.
- Approximate areas under $g'$ between 2 and 5: Negative area from $2$ to $3$, then slight increase but overall negative, so unlikely to be zero.
- Cannot guarantee $g(2) = g(5)$.
17. Conclusion for 18: Only statement II must be true; answer (B).
Final answers:
16: (D)
17: (B)
18: (B)