Let be differentiable at and . If , then at is:
- (A)differentiable if ✓ Correct
- (B)differentiable if
- (C)not differentiable
- (D)not differentiable if
Answer: (A)
Solution
Consider at a point where . Near , , so . If the right- and left-hand limits disagree and is not differentiable, whereas if the limit is . So is differentiable at exactly when .
JEE Main · 2019 · 10 Apr 2019 · Shift 1 · Single correct option