Differentiability Graph B59A03
1. **Problem Statement:** We are given a function $f$ with a vertical tangent at $x=4$, a horizontal tangent at $x=5$, a jump discontinuity at $x=2$, and a removable discontinuity at $x=7$. We need to identify which statement about differentiability is false.
2. **Recall Differentiability Rules:**
- A function is **not differentiable** at points where it has discontinuities (jump or removable).
- A function is **not differentiable** at points where the tangent is vertical because the derivative tends to infinity or is undefined.
- A function **is differentiable** at points where the tangent is horizontal, as the derivative is zero but defined.
3. **Analyze Each Statement:**
- (A) At $x=2$, there is a jump discontinuity, so $f$ is not differentiable there. This is **true**.
- (B) At $x=4$, there is a vertical tangent, so $f$ is not differentiable there. This is **true**.
- (C) At $x=5$, there is a horizontal tangent. The derivative exists and equals zero, so $f$ is differentiable there. The statement claims $f$ is not differentiable, so this is **false**.
- (D) At $x=7$, there is a removable discontinuity, so $f$ is not differentiable there. This is **true**.
4. **Conclusion:** The false statement is (C).
**Final answer:** Statement (C) is false because a horizontal tangent at $x=5$ means the function is differentiable there.