$-(2.27)^{\frac 13}+6.(2.27)^{-\frac 13}-4^{\frac 13}=-(2.3^3)^{\frac 13}+6.(2.3^3)^{-\frac 13}-4^{\frac 13}=-3.2^{\frac 13}+6.3^{-1}.2^{-\frac 13}-4^{\frac 13}$
$=-3.2^{\frac 13}+2.2^{-\frac 13}-4^{\frac 13}=-3.2^{\frac 13}+2^{\frac 23}-2^{\frac 23}=-3.2^{\frac 13}$