If we have $f$ is differentiable on $(a,b)$, and continuous on $[a,b]$, then
for any $x\in (a,b)$, exists $y, z \in [a,b]$, such that
Is this right?
No. Consider $f(x)=x^3$ on the interval $[-1,1]$ with $x=0$.
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3 years ago