If a function f:[a,b]→Rf : [a,b] \to \mathbb{R}f:[a,b]→R is differentiable at [a,b][a,b][a,b], there exists a c∈(a,b)c \in (a,b)c∈(a,b) such that y0=f′(c)y_{0} = f ' (c)y0=f′(c) is satisfied between f′(a)f ' (a)f′(a) and f′(b)f ' (b)f′(b) for some y0y_{0}y0.
