请帮忙做道高数的题，谢谢

sin(xy)-1/y-x=1
x=0,y=-1
[sin(xy)-1/y-x]'=0
cos(xy)*(y+xy')-1/y^2*y'-1=0
y'=[1-y*cos(xy)]/[xcos(xy)-1/y^2]
y'(0)=2/(-1)=-2

两边x对求导得：
cos(xy)*(y+xy')-y'/y2-1=0
由x=0时y=-1.
把这代入得：
cos0*(-1+0)-y'/1-1=0
可得，y'(0)=-2