Show that the function
is continuous but not differentiable at x=3.

Let c be a real number.
Case I: c<3 Then f(c) = 3-c.
CaseII: c = 3. Then f(c) = 3 - 3 = 0

Since

f is continuous at x = 3.
Case III: C>3. Then f(c) = c - 3

Since,

Therefore, f is a continuous function.
Now, we need to show that

Consider the left hand limit of f at x = 3

Consider the right hand limit of f at x = 3


Since the left and right hand limits are not equal, f is not differentiable at x = 3.