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f(x,y)=3(x+y)+32xy f(x,y)=3(x+y)-32xy f(x,y)=3(x+y)-16xy f(x,y)=3(x+y)+16xy
f(x,y)=3(x+y)-32xy f(x,y)=3(x+y)-16xy f(x,y)=3(x+y)+32xy f(x,y)=3(x+y)+16xy
f(x,y)=3(x+y)+32xy f(x,y)=3(x+y)-32xy f(x,y)=3(x+y)-16xy f(x,y)=3(x+y)+16xy
a y a x y f x f a y a x x f y f y f x f yx x f y f yx
f(xy)=f(x)f(y) f(xy)=f(x)+f(y) f(x+y)=f(x)f(y) f(x+y)=f(x)+f(y)
a y a x y f x f a y a x x f y f a y a x y f x f 22 a y a x x f y f 22
f(x,y)=3(x+y)+32xy f(x,y)=3(x+y)-32xy f(x,y)=3(x+y)-16xy f(x,y)=3(x+y)+16xy
x+y﹣3=0 x﹣y﹣2013=0 x﹣y﹣2015=0 x﹣y+2017=0
f(x,y)=3(x+y)+32xy f(x,y)=3(x+y)-32xy f(x,y)=3(x+y)-16xy f(x,y)=3(x+y)+16xy
f(xy)=f(x)f(y) f(xy)=f(x)+f(y) f(x+y)=f(x)f(y) f(x+y)=f(x)+f(y)
f(-x,-y)=f(x,y). f(-x,-y)=-f(x,y). f(-x,-y)=f(x,-y)=-f(x,y). f(-x,-y)=f(x,-y)=f(x,y).
,y∈ ,(A.⊆R,B.⊆R)有唯一确定的f(x,y)与之对应,则称f(x,y)为关于x,y的二元函数.满足下列性质的二元函数f(x,y)称为关于实数x,y的广义“距离”: (1)非负性:f(x,y)≥0,当且仅当x=y时取等号; (2)对称性:f(x,y)=f(y,x); (3)三角形不等式:f(x,y)≤f(x,z)+f(z,y)对任意的实数z均成立. 今给出三个二元函数:①f(x,y)=|x-y|;②f(x,y)=(x-y)2;③f(x,y)=. 其中能够成为关于x,y的广义“距离”的二元函数的序号是( ) A.①B.①② ②③ ①②③
z=f(x,y)在点(x0,y0)处可微,则f(x,y)在点(x0,y0)处连续 z=f(x,y)在点(x0,y0)处可微,则f(x,y)在点(x0,y0)处可导 z=f(x,y)在点(x0,y0)处可导,则f(x,y)在点(x0,y0)处可微 z=f(x,y)在点(x0,y0)处偏导数连续,则f(x,y)在点(x0,y0)处连续