般地设 w= f(x 19~29 Ow_lim ∫(x1,…,x1+Ax1,…,xn)-f(x1 v;→>0一般地 设 ( , , , ) x1 x2 xn w = f  i i i n i n x i x f x x x x f x x x x w i    ( , , , , ) ( , , , , ) lim 1 1 0  +  −   =   → (i = 1,2,  ,n)