Let . If is differentiable at , what is the value of ?
Answer and explanation
Correct answer: B.
- Step 1: For to be differentiable at , it must be continuous at : .
- Step 2: Differentiability requires matching left-hand and right-hand derivatives at : , and . Equating them gives .
- Step 3: Substitute into the continuity equation: . Then evaluate .
Answer
.
Why not the others: Other values enforce continuity but ignore differentiability at the interface , or make arithmetic sign slips.
Practise more Basic results.
Free questions with an explanation for every one, and full timed AP (Advanced Placement) mock tests.