z=x^3y+5x^2y^3dz=3x^2dx*y+x^3dy+5*2xdx*y^3+5x^2*3y^2dy=(3x^2y+10xy^3)dx+(x^3+15x^2y^2)dy则:z|'x=(3x^2y+10xy^3)z|'y=(x^3+15x^2y^2)所:z|''x=3y*2x+10y^3=6xy+10^3.z|''y=15x^2*2y=30x^2yz|''xy=3x^2+10x*3y^2=3x^2+30xy^2.
z=x^3y+5x^2y^3
dz=3x^2dx*y+x^3dy+5*2xdx*y^3+5x^2*3y^2dy
=(3x^2y+10xy^3)dx+(x^3+15x^2y^2)dy
则:
z|'x=(3x^2y+10xy^3)z|'y=(x^3+15x^2y^2)
所:
z|''x=3y*2x+10y^3=6xy+10^3.
z|''y=15x^2*2y=30x^2y
z|''xy=3x^2+10x*3y^2=3x^2+30xy^2.