Let $\lambda$$^ * $ be the largest value of $\lambda$ for which the function ${f_\lambda }(x) = 4\lambda {x^3} - 36\lambda {x^2} + 36x + 48$ is increasing for all x $\in$ R. Then ${f_{{\lambda ^ * }}}(1) + {f_{{\lambda ^ * }}}( - 1)$ is equal to :