Factor - 7x3+21x2+3x-9 by grouping what is the resulting expression

Factor Group 1

-7x^3 + 21x^2

-7x^2 (x - 3)

Factor Group 2

3x - 9

3 (x - 3)

As you can see, there are two

(x - 3) factors. We only need one of them in the final answer as one of the factors.

Answer: (-7x^2 + 3) (x - 3)

Done!