# Thread: Problem of the Week #293 - Dec 31, 2019

1. Here is this week's POTW:

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Suppose $f : (a,b) \to \Bbb R$ is a convex function. Show that $f$ is differentiable at all but countably many points and the derivative is nondecreasing.

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Remember to read the "POTW submission guidelines to find out how to "submit your answers!

2.

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