设f(x,y)＝√(x^3+y^3),x0＝1,y0＝2,x＝1.02,y＝1.97αf/αx＝3x^2/[2√(x^3+y^3)],αf/αy＝3y^2/[2√(x^3+y^3)]代入x0＝1,y0＝2,得αf/αx＝1/2,αf/αy＝2√((1.02)^3+(1.97)^3)＝f(x,y)≈f(x0,y0)＋αf/αx(x-x0...