∂z/∂x=yf1'+(1/y)f2' 里面的1,2全是下标
∂²z/∂x∂y=f1' + y[xf11''-(x/y²)f12''] - (1/y²)f2' + (1/y)[xf21''-(x/y²)f22'']
=f1' - (1/y²)f2' + xyf11'' - (x/y³)f22''
希望可以帮到你,如果解决了问题,请点下面的"选为满意回答"按钮,
∂z/∂x=yf1'+(1/y)f2' 里面的1,2全是下标
∂²z/∂x∂y=f1' + y[xf11''-(x/y²)f12''] - (1/y²)f2' + (1/y)[xf21''-(x/y²)f22'']
=f1' - (1/y²)f2' + xyf11'' - (x/y³)f22''
希望可以帮到你,如果解决了问题,请点下面的"选为满意回答"按钮,