If \({\rm{f}}\left( {{\rm{x}} + {\rm{iy}}} \right) = {{\rm{x}}^3}-3{\rm{x}}{{\rm{y}}^2} + {\rm{i}}\phi {\rm{\;}}\left( {{\rm{x}},{\rm{\;y}}} \right)\) where \({\rm{i}} = \sqrt { - 1} \) and \({\rm{f}}\left( {{\rm{x\;}} + {\rm{\;iy}}} \right)\) is an analytic function then \(\phi {\rm{\;}}\left( {{\rm{x}},{\rm{\;y}}} \right)\) is
1
\({{\rm{y}}^3} - 3{{\rm{x}}^2}{\rm{y}}\)
2
\(3{{\rm{x}}^2}{\rm{y}} - {{\rm{y}}^3}{\rm{\;}}\)
3
\(3{{\rm{x}}^2}{\rm{y}} - {{\rm{x}}^3}\)
4
\({{\rm{x}}^3} - 3{{\rm{x}}^2}{\rm{y}}\)