Question 181641
5x^2y^3 -15x^3y^2

(1)notice that 5 and -15 both have common factor of 5
(2)notice that x^2 and x^3 both have common factor of x^2
(3)notice that y^3 and y^2 both have common factor of y^2

start by taking out factor and inside parenthesis leaving what is left

5x^2y^2(1y - 3x)

or 

5x^2y^2(y-3x)