Let # f(x) = x^3 - e^-x #
Then # f(0) = 0-e^0 = -1 #
And, # f(1) = 1 - e^-1 = 0.6321 # (4dp)
Both #e^-x# and # x^3 # are continuous functions # AA x in RR #, and hence # f(x) = x^3 - e^-x # is a continuous function # AA x in RR #. As #f(x)# changes sign over the interval #[0,1]# then #f(x)=0# must have a root in that interval, and consequently #e^-x=x^3 # has a solution in the interval.