When multiplying y ^2 by y^-2 do you add the exponents? If so that would be zero correct?
Yes, you are right, Nicholas; the rule for multiplying two exponential terms with the same base is:
yayb = ya+b
So, yes, you are right again:
y2y-2 = y2+(-2) = y0
Now what does y0 = ? (Hint: it's not zero)