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提问人:网友黄平
发布时间:2022-01-07
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[单选题]
设函数z=f(x,y)在(x,y)处可微,则下列等式正确的是()
A.
B.
C.
D.
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A.
B.
C.
D.
设函数z=f(x,y)在点(1,1)处可微,且f(1,1)=1,设φ(x)=f(x,f(x,x)).求
若z=f(x,y)在(x0,y0)处存在偏导数。则下列说法正确的是( )
A.z=f(x,y)在(x0,y0)处连续
B.z=f(x,y)在(x0,y0)处可微
C.若(x0,y0)是f(x,y)的驻点,则一定是f(x,y)的极值点
D.若(x0,y0)是z=f(x,y)的极值点,则必有f'x(x0,y0)=f'y(x0,y0)=0
设z=f(x,y)在(x0,y0)处的全增量为△z,若z=f(x,y)在(x0,y0)处可微,则在(x0,y0)处( )
A.△z=dz B. △z=fx△x+fy△y
C.△z=fxdx+fydy D.△z=dz+η(η为高阶无穷小)
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