(2006)曲面z=1-x2-y2在點處的切平面方程是:()
A. B. C. D.
(2006)已知函數(shù)等于:()
A.2x+2y B.x+y C.2x-2y D.x-y
A.2x-2y B.2xdx-2ydy C.f′(x2-y2)dx D.2f′(x2-y2)(xdx-ydy)