z=y²ln(x²+y²)那么z对x求偏导数得到y²*1/(x²+y²)*2x即2xy²/(x²+y²)而对y求偏导数得到2y*ln(x²+y²)+y²*1/(x²+y²)*2y即2y*ln(x²+y²)+2y^3*1/(x²+y²)
