4x^1/4(-3x^1/4y^1/3)/（-6x^-1/2y-2/3）
=4*(-3)/(-6)*(x^1/4*x^1/4/x^-1/2)*(y^1/3/y^-2/3)
=2x^[1/4+1/4-(-1/2)]y^[1/3-(-2/3)]
=2xy