It wasn't easy but me and my friend got it. This is the expansion and simplification to get to the desired answer. You need to move the denominator to the top, thereby changing the power to a negative, and then use the binomial expansion formula for both top and bottom. You should be able to get it.

As for the range, X just has to not be -1 or else the expression won't be valid, since you'll be dividing by 0.

As for the second part, make the fraction inside the bracket equal to 19/20. Solve for X, and you will get 1/39. With the fourth root being n=1/4, substitute these values in the simplified equation and get your fraction. Give it a try. Hope it helps!