Given f is differentiable on $(a,b)$, continuous on $[a,b]$ and f(a)=f(b)=0, then is this true that $f'(c)=f(c)$ for some $c\in(a,b)$?. Intuitively i feel this statement is true, so I tried to use mean value theorem for some combination of functions like adding and composing f with other functions etc, but i am unable to prove.
Do derivative always coincide with the function at some point?
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$\begingroup$
calculus
derivatives
continuity
1 Answers
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This follows from Rolle's theorem applied to the function $-e^{-x} f(x)$ which has derivative $$e^{-x} (f(x) - f'(x)).$$
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0Nicely done. Welcome to the site! (+1) – 2017-01-19