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

Discussion

Which of the following is NOT true?

  • A.Every differentiable function is continuous
  • B.Every continuous function is differentiable
  • C.The function \(f: \mathbb{R} \to \mathbb{R},\ f(x) = |x| + \sin|x - 3|\) is continuous
  • D.The function \(f: \mathbb{R} \to \mathbb{R},\ f(x) = |x| + \sin|x - 3|\) is not differentiable at \(x = 0, 3\)

Answer: B

The statement that is not true is that every continuous function is differentiable. The function \(f(x) = |x|\) is continuous at \(0\) but has a corner there, so its derivative does not exist at \(0\). The opposite statement, that every differentiable function is continuous, is a standard theorem and is true.


The function \(|x| + \sin|x-3|\) is a sum of continuous functions, so it is continuous, and it has corners at \(x = 0\) and \(x = 3\) where the absolute values change sign, so it is not differentiable there. Both of those statements are true, which leaves option B as the false one.

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

Post your comment

Please log in or register to post a comment.