不能推出:一阶偏导数在该点也连续
反例如下:
f(x,y)=exp(x*y)/y^(3/2) (y!=0),
f(x,0)=0
则:df/dx=exp(x*y)/y^(1/2)
d^2f/dx^2=y^(1/2)*exp(x*y)
y^(1/2)*exp(x*y)连续.
exp(x*y)/y^(1/2)不连续
不能推出:一阶偏导数在该点也连续
反例如下:
f(x,y)=exp(x*y)/y^(3/2) (y!=0),
f(x,0)=0
则:df/dx=exp(x*y)/y^(1/2)
d^2f/dx^2=y^(1/2)*exp(x*y)
y^(1/2)*exp(x*y)连续.
exp(x*y)/y^(1/2)不连续