设函数f(u,v)具有一阶连续偏导数,且f(x+y,x-y)=4(x2-xy-y2)
题型:单项选择题
问题:
设函数f(u,v)具有一阶连续偏导数,且f(x+y,x-y)=4(x2-xy-y2),则xf’x(x,y)+yf’y(x,y)=
(A) 2x2-8xy一2y2. (B) -2x2+8xy-2y2.
(C) 2x2-8xy+2y2. (D) -2x2+8xy+2y2.
设函数f(u,v)具有一阶连续偏导数,且f(x+y,x-y)=4(x2-xy-y2),则xf’x(x,y)+yf’y(x,y)=
(A) 2x2-8xy一2y2. (B) -2x2+8xy-2y2.
(C) 2x2-8xy+2y2. (D) -2x2+8xy+2y2.