Final answer:
The given recursive formula and the term a4=870 do not allow for a solution where a4 can be generated by squaring the previous term and subtracting it. Therefore, none of the provided options for the first two terms of the sequence are correct under the given conditions.
Step-by-step explanation:
To find the first two terms of the sequence where the recursive formula is given by an = (an-1)2 - an-1, and we're told a4 = 870, we will work backwards using the formula.
Let's find a3. Assuming a3 is the square root of 870 plus 1, to satisfy the formula an = (an-1)2 - an-1. Unfortunately, 870 is not a perfect square, and therefore there isn't a whole number that we can square and subtract itself to get 870. Hence, we conclude there must be an error in the formula or the terms provided. None of the options given would satisfy the recursive formula if a4 = 870.
This sequence does not seem to match a typical series expansion such as the binomial theorem. More information or clarification might be needed to proceed.