As we know that,\\\\(V{\\left( X \\right)} = E{\\left( {X}^{2} \\right)} - {\\left( E{\\left( X \\right)} \\right)}^{2}\\\\)\\\\(\ herefore 6 = E{\\left( {X}^{2} \\right)} - {5}^{2}\\\\)\\\\(\\Rightarrow E{\\left( {X}^{2} \\right)} = 6 + 25 = 31\\\\)