Hi there, I need some help in this problem!

Expand (1+xy)^n in ascending powers of y as far as y^2, where n is not a positive integer and x is a positive real number. State in terms of x , the range of values of y for which the expression is valid.

Find the values of x and n if (1 + xy)^n ~ 1+y-y^2. Ans: n=1/3, x=3

By replacing a suitable value for y, find an approximate value of 5^(1/3) Ans: 1 21/29