9k^2 +66k + 21 factoring trinomials
\(9k^2 +66k + 21 \\ \\ GCF = 3 \\ \\ 3( \frac{9k^2}{3} + \frac{66k}{3} + \frac{21}{3}) \\ \\ 3(3k^2 + 22k + 7) \\ \\ 3(3k^2 + 21k + k + 7) \\ \\ 3(3k(k+7) + (k+7)) \\ \\ 3(k+7)(3k+1) \\ \\ Answer: \fbox {3(k+7)(3k+1)}\)
