Limit Continuity 7B1845
1. **Problem Statement:** Given that $$\lim_{x \to 3} f(x) = 7$$, determine which of the following statements must be true:
I. $$f$$ is continuous at $$x=3$$
II. $$f$$ is differentiable at $$x=3$$
III. $$f(3) = 7$$
Options:
A) None
B) II only
C) III only
D) I and III only
E) I, II, and III
2. **Recall the definitions and rules:**
- The limit $$\lim_{x \to a} f(x) = L$$ means as $$x$$ approaches $$a$$, $$f(x)$$ approaches $$L$$.
- $$f$$ is continuous at $$x=a$$ if and only if:
$$\lim_{x \to a} f(x) = f(a)$$
- Differentiability at $$x=a$$ implies continuity at $$x=a$$, but continuity does not imply differentiability.
3. **Analyze each statement:**
- Statement I (Continuity): For $$f$$ to be continuous at $$x=3$$, we need $$\lim_{x \to 3} f(x) = f(3)$$.
- Statement III: $$f(3) = 7$$ is not guaranteed by the limit alone; the function value at 3 could be different or undefined.
- Statement II (Differentiability): Differentiability requires continuity and more (smoothness), so it is not guaranteed by the limit alone.
4. **Conclusion:**
- Since $$\lim_{x \to 3} f(x) = 7$$, the limit exists and equals 7.
- But $$f(3)$$ may or may not equal 7, so continuity (I) and $$f(3) = 7$$ (III) are not guaranteed.
- Differentiability (II) is also not guaranteed.
Therefore, none of the statements must be true based solely on the given limit.
**Final answer:** A) None