a. Suppose f is twice differentiable on (0, infinity). Suppose that |f(x)|< or equal A0 for all x>0 and that the second derivative satisfies |f''(x)|< or equal A2 for all x>0.(adsbygoogle = window.adsbygoogle || []).push({});

Prove that for all x>0 and all h>0

|f'(x)| < or equal 2A0/h + A2h/2

This is sometimes called Landau's inequality.

b. Use part a to show that for all x>0

|f'(x)| < or equal 2 sqrt(A0A2)

I have no idea how to go about this problem.

Should I just try to do this problem backwards by trying to find what f(x) by using the f'(x)?

Thanks

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# Homework Help: Twice differentiability

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