Hey, just need some help with a fraction simplification problem.

how can i make [k(k+1)(k+2)]/3 + (k+1)(k+2) = (k+1)(k+2)(k/3 + 1)

and then take that step and have it equal [(k+1)(k+2)(k+3)]/3

i slightly understand the second to third step but not how to go from the first to the second (factor out a k but how?) thanks.