What is the factorization of the polynomial below? - 3x^3+15x^2+42x

Factoring out x

x (-3x^2+15x+42) now factor parenthetical expression

x (-3x^2+21x-6x+42)

x (-3x (x-7) - 6 (x-7))

x (-3x-6) (x-7) we can factor out - 3 from first parentheses

-3x (x+2) (x-7)