Factor the gcf: -6x^4y^5 - 15x^3y^2 + 9x^2y^3

-6x^4y^5 - 15x^3y^2 + 9x^2y^3

-6x^4y^5 =  -2, 3, x, x, x, x,  y, y, y, y, y
15x^3y^2 =  -5, 3 x, x, x, y, y
9x^2y^3 =    3, 3 x, x, y, y, y

Each group has a 3 in common and each group has 2 x in common and each group has 2 y in common so the GCF = -3x^2y^2

Divide that out and we get