f(x)在x=c处的左极限是ac+b,右极限是c²f(x)在x=c处可导必连续,得ac+b=c² (1)f(x)在x=c处的左导数是a,右导数是2cf(x)在x=c处可导,得a=2c (2)由(1)(2)解得a=2c,b=-c²所以 a=2c,b=-c²
