where λ is general Lagrange multiplier which can be identified via variational theory, u0(t) is an initial approximation with possible unknowns, and un is considered as restricted variation [15] (i.e.,δ un = 0). Therefore, we first determine the Lagrange multiplier λ that will be identified optimally via integration by parts. The successive approximations un+1(t) of the solution u(t) will be readily obtained upon using the obtained Lagrange multiplier and by using any selective function u0. Consequently, the exact solution may be obtained by u=limn→∞un.