y->0+
(1- y^3)^(1/3) = 1-(1/3)y^3 +o(y^3)
1-(1- y^3)^(1/3) = (1/3)y^3 +o(y^3)
lim(x->∞) [ x+(1-x^3)^(1/3)]
y=1/x
=lim(y->0+) [ 1/y+(1-1/y^3)^(1/3)]
=lim(y->0+) [ 1+(y^3-1)^(1/3) ] /y
=lim(y->0+) [ 1-(1- y^3)^(1/3) ] /y
=lim(y->0+) (1/3)y^3 /y
=0