(x^3 + y^2) (x^3 - y^2)=?
When you see identical terms in two binomials and the signs are one plus and one minus (or one minus and then one plus), you have "the difference of squares." All you have to do is square the first and second terms and put a minus sign between them. (x^3+y^2)(x^3-y^2)= x^6-y^4. That's it!
You could, of course, multiply it all out, but the middle terms will cancel: x^6 - x^3y^2 + x^3y^2 - y^4 gives you the same answer. To multiply it out, just have each term in the first ( ) "dance" with each term in the second ( ).
Hope this helped!