I am asked to expand and simply the following expression.

(x + √2)7 + (x - √2)7

I have my notes here on the binomial theorem, and it seems simply enough to expand each of those terms.....except.

In my notes it says

(x+y)^n= then goes on the expand here with each term added to the next.

It does not mention anything about...

(x-y)^n ?

Is it the same as addition except each term is subtracted from the next?