單項(xiàng)選擇題

(2006)已知函數(shù)等于:()

A.2x+2y
B.x+y
C.2x-2y
D.x-y


你可能感興趣的試題

1.單項(xiàng)選擇題(2009)設(shè)z=f(x2-y2),則dz等于:()

A.2x-2y
B.2xdx-2ydy
C.f′(x2-y2)dx
D.2f′(x2-y2)(xdx-ydy)

2.單項(xiàng)選擇題(2010)下列各點(diǎn)中為二元函數(shù)z=x3-y3-3x2+3y-9x的極值點(diǎn)的是:()

A.(3,-1)
B.(3,1)
C.(1,1)
D.(-1,-1)

3.單項(xiàng)選擇題(2011)若函數(shù)f(x,y)在閉區(qū)域D上連續(xù),下列關(guān)于極值點(diǎn)的陳述中正確的是:()

A.f(x,y)的極值點(diǎn)一定是f(x,y)的駐點(diǎn)
B.如果P0是f(x,y)的集值點(diǎn)。P0點(diǎn)處B2-AC<0(其中,
C.如果P0是可微函數(shù)f(x,y)的極值點(diǎn),則在P0點(diǎn)處df=0
D.f(x,y)的最大值點(diǎn)一定是f(x,y)的極大值點(diǎn)