A.必要條件 B.充分條件 C.充要條件 D.無關(guān)條件
(2006)曲面z=1-x2-y2在點(diǎn)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