  The shifted-i expansion technique (SLET) is extended to solve for Dirac
particle trapped in spherically symmetric scalar and/or 4-vector potentials. A
parameter {\lambda}=0,1 is introduced in such a way that one can obtain the
Klein-Gordon (KG) bound states from Dirac bound states. The 4-vector Coulomb,
the scalar linear, and the equally mixed scalar and 4-vector power-law
potentials are used in KG and Dirac equations. Exact numerical results are
obtained for the 4-vector Coulomb potential in both KG and Dirac equations.
Highly accurate and fast converging results are obtained for the scalar linear
and the equally mixed scalar and 4-vector power-law potentials.
