Answer:

Explanation:
You are given the roots 1, -1, and 2.
From there, you can combine all these factors into:
(x-1)(x+1)(x-2)
You know this because if you set these factors to 0, it will give you the roots 1, -1, and 2.
You can find the answer by multiplying all the factors and you get:

Hope I helped :)