00:03
Here we have f of x is a piecewise defined function when x is less than three, f of x equals this expression.
00:11
When x is greater than or equal to three, f of x equals this expression.
00:16
We have to find f prime of three, and by now you know that means since three is, you know, the dividing point for this function, you know that that entails finding the left -hand limit of the difference quotient and the right -hand limit.
00:33
Of the difference quotient.
00:35
But we're going to save a whole lot of work in this particular problem because one of the theorems that you've learned in this section is if a function is differentiable at a point a, then it's continuous at a.
00:50
And so if the function is not continuous at a point a, then it's not going to be differentiable at a.
00:58
If we can show that this function is not continuous at 3, then f, prime of 3 will not exist because f would not be differentiable at 3.
01:08
And that's pretty easily done...