两边求导1+5xy²+5x²yy'-3y'=01+5xy²=y'(3-5x²y)y'=(1+5xy²)/(3-5x²y)将(1，1)代入y'=(1+5)/(3-5)=-3即切线斜率为-3切点为(1，1)所以切线方程y-1=-3(x-1)整理得y=-3x+4法线方程y-1=(1/3)(x-1)y=x/3+2/3
