Suppose h:R⟶R is differentiable everywhere and h′ is continuous on [0,1], h(0)=−2 and h(1)=1. Show that:
|h(x)|≤max(|h′(t)|,t∈[0,1]) for all x∈[0,1]
I attempted the problem the following way:
Since h(x) is differentiable everywhere then it is also continuous everywhere. h(0)=−2 and h(1)=1 imply that h(x) should cross x-axis at some point (at least once). Denote that point by c to get h(c)=0 for some c∈[0,1].
h′(x) continuous means that lim[h′(x)]=h′(a) as x→a but then I am stuck and I don't see how what I have done so far can help me to obtain the desired inequality.
Thank you in advance!
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