Đáp án:
1, `3x . 4/3 x^2y`
` = (3 . 4/3)(x x^2)y`
` = 4x^3y`
2, `-9xy^2 . -1/3 x^3y`
` = (-9 . -1/3)(x x^3)(y^2 y)`
` = 3x^4y^3`
3, `3\sqrt{2}xy^4 . \sqrt{2}x^4y`
` = ( 3 \sqrt{2} . \sqrt{2})(x x^4)(y^4y)`
` = 6x^5y^5`
4, `-6x^2y . (3x^2y^2)^2`
` = -6x^2y . 9x^4y^4`
` =(-6 . 9)(x^2 x^4)(yy^4)`
` = -54x^6y^5`