integrate by using i= 1 and 2

The above expression becomes, from (5.10), b u; = (x)-(1)dxif((1-2)++) +3 dx3, (4.16) where x = x-x, X=2, X3 = x3. By using (4.10) the integrations in (4.16) can be done easily, leading to (4.13) and (4.14).