To find out this question we start to split up the interval $ \displaystyle \left[ {a,b} \right]$ into a finite number of intervals.

$ \displaystyle \left[ {{{x}_{0}},{{x}_{1}}} \right],\left[ {{{x}_{1}},{{x}_{2}}} \right],……..\left[ {{{x}_{{n-1}}},{{x}_{n}}} \right]$ with $ \displaystyle a={{x}_{0}}<{{x}_{1}}<……..<{{x}_{n}}=b$

This breaks up the region $ \displaystyle \Omega $ into n subregions: $ \displaystyle {{\Omega }_{1}},{{\Omega }_{2}},……{{\Omega }_{n}}$