方程两边对x求导得 2x+y′ x2+y =3x2y+x3y′+cosxy′= 2x?(x2+y)(3x2y+cosx) x5+x3y?1 由原方程知,x=0时y=1,代入上式得y′|x=0= dy dx |x=0=1故答案为:1