Final answer:
The number of terms in the expansion is four. The first term in the expansion is 2x^15.
Step-by-step explanation:
The given expression is: 2x15 + 215x15 + 10y15 + 1015y
To determine the number of terms in this expansion, we count the different terms. In this case, there are four different terms: 2x15, 215x15, 10y15, and 1015y.
The first term in this expansion is 2x15. It is the term that comes first when the expression is written in standard form.