Resposta:

-x^3 y^3

[tex]( - xy).( - xy).( - xy) = \\ ( - xy) \times ( - xy) \times ( - xy) \\ - xyxyxy \\ ( - xy) \times ( -xy) \times( - xy) \\ - xyxyxy \\ - x {}^{3}y \times y \times y \\ - xyxyxy \\ - x {}^{3}y \\ ( - xy) \times ( - xy) \times (xy) \\ - x {}^{3}y {}^{3} \\ resposta \\ - x {}^{3}y {}^{3} [/tex]