Mean value theorem by maple 13

  Hi there,

  I want to use maple 13 for calculating mean value theorem for differentiable function  f:=piecewise(-2≤x≤0, -x² ,0≤x≤2,x²) 

on the interval [-2,2]. But an error occured, that is,"function must be continuous".Any help will be appreciated.

REGARDS

 Yegan