Question

xy²-x²y, para x = -1/2 e y = 2/3

Answer 1

[-1/2.(2/3)² ]- [(-1/2)².2/3]=
[-1/2*4/9] - [1/4*2/3]=
-4/18 - 2/12=
(-8-6)/36=
-14/36= -7/18

Answer 2

$xy^2 - x^2y$

para 

x = $- \dfrac{1}{2}$

y = $\dfrac{2}{3}$

$- \dfrac{1}{2}* (\dfrac{2}{3})^2 -(- \dfrac{1}{2})^2* \dfrac{2}{3} \\ \\ \\ - \dfrac{1}{2}* \dfrac{4}{9} - \dfrac{1}{4}* \dfrac{2}{3} \\ \\ \\ - \dfrac{2}{9} - \dfrac{1}{6} \\ \\=> - \dfrac{7}{18}$