Answer:
(r + 14)
Explanation:
When factoring a trinomial in the form of:
you need to find 2 numbers that multiply to make ac and add to make b. Here, we need to find 2 numbers that multiply to 98 and add to 21. First, list the factors of 98:
1, 98
2, 49
7, 14
and the reverse of all of those is also true.
Now find factors that add to 21. In this case, those are 7 and 14. You need to break the middle term in the trinomial into those 2 numbers:
Finally, you can factor each half of this individually.
We were already given (r + 7), so the answer is (r + 14).