Question

(x^2 + y^2)^3

Answer 1

Do you know how to expand (x+y)^3 ?

Answer 2

You could do that by writing (x+y)^3 as (x+y)(x+y)(x+y) and then multply all the x's and y's between each pair of brackets, giving 9 terms in all. Some of these terms can be collected. The result is:
\[(x+y)^3=x^3+3x^2y+3xy^2+y^3\]

Now if you try, you can do the same with x² and y²...

Answer 3

I guess it is clear now.

Answer 4

Only, someone has something left to do now ;)