Machine-translated by Google. Questions are authored in English.
Top

Discussion

True or false: a function may have a derivative at a point without being continuous there.

  • A.True, whenever the one-sided derivatives agree in value
  • B.True, if the function is bounded near the point
  • C.False, differentiability requiring continuity as a precondition
  • D.True, provided the discontinuity is removable

Answer: C

The difference quotient \( [f(x)-f(a)]/(x-a) \) can only tend to a finite limit if the numerator tends to zero, which is continuity at \( a \). So differentiability is strictly the stronger condition, and a discontinuity of any kind, removable or not, rules the derivative out

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.