Although I hate to agree with someone who does work for someone over pointing them in the right direction, I believe that Elisha is right here.

If you look at Pascal's triangle, you will see that on the 9th row from the top, in the center is 70. (we ignore the top row for expansion)

Pascal's triangle follows the same pattern as the coefficients for binomial expansion.

The (x/y)^4(y/x)^4 is the easy part to work out.

Elisha, regarding my problem with you providing complete answers:

1. please read

**This Announcement** which gives the site's policy on homework help. If a question is obviously homework, please refrain from posting a complete answer, this helps the poster to learn and

**do their work for themselves**.

2. If you have to post a complete answer, please do more to explain your working and lay it out properly, this can be done by entering more line breaks in your working, and writing a little more, this will help contribute to the site much further, and will help the poster more.