For this case we have the following polynomials:
6x ^ 7 + 9x ^ 3 - x + 9
2x ^ 7 + 7x ^ 6 + 6
Adding we have:
(6x ^ 7 + 9x ^ 3 - x + 9) + (2x ^ 7 + 7x ^ 6 + 6)
We group in similar terms:
x ^ 7 (6 + 2) + x ^ 6 (7) + x ^ 3 (9) + x (-1) + (9 + 6)
Rewriting we have:
8x ^ 7 + 7x ^ 6 + 9x ^ 3 - x + 15
Answer:
8x ^ 7 + 7x ^ 6 + 9x ^ 3 - x + 15
option C