Injective map that is not an immersion

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I am studying analysis and I have had a lot of uncertainties. For instance, I cannot solve this exercise:



If $f:UrightarrowmathbbR^3$ has class $C^1$ and rank $3$ in all of the points of the open $UinmathbbR^4$, show that $|f(x)|$ do not assume maximal value for $xin U$.



(I guess this is the comand, but I'm so sorry if I did mistakes. My language and the language of the comand is Portuguese)



Well. I know that $f$ is a submersion. So, it's an open map. From here can I get the required? If I know that $f$ is an open map, have I that $|f(x)|$ is an open set and so that it has not a maximum?







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  • Your second paragraph makes no sense to me.
    – zhw.
    Jul 16 at 20:08










  • Sorry, I did a mistake and I hope now the question is correct. Thanks.
    – Na'omi
    Jul 16 at 21:52















up vote
0
down vote

favorite
1












I am studying analysis and I have had a lot of uncertainties. For instance, I cannot solve this exercise:



If $f:UrightarrowmathbbR^3$ has class $C^1$ and rank $3$ in all of the points of the open $UinmathbbR^4$, show that $|f(x)|$ do not assume maximal value for $xin U$.



(I guess this is the comand, but I'm so sorry if I did mistakes. My language and the language of the comand is Portuguese)



Well. I know that $f$ is a submersion. So, it's an open map. From here can I get the required? If I know that $f$ is an open map, have I that $|f(x)|$ is an open set and so that it has not a maximum?







share|cite|improve this question





















  • Your second paragraph makes no sense to me.
    – zhw.
    Jul 16 at 20:08










  • Sorry, I did a mistake and I hope now the question is correct. Thanks.
    – Na'omi
    Jul 16 at 21:52













up vote
0
down vote

favorite
1









up vote
0
down vote

favorite
1






1





I am studying analysis and I have had a lot of uncertainties. For instance, I cannot solve this exercise:



If $f:UrightarrowmathbbR^3$ has class $C^1$ and rank $3$ in all of the points of the open $UinmathbbR^4$, show that $|f(x)|$ do not assume maximal value for $xin U$.



(I guess this is the comand, but I'm so sorry if I did mistakes. My language and the language of the comand is Portuguese)



Well. I know that $f$ is a submersion. So, it's an open map. From here can I get the required? If I know that $f$ is an open map, have I that $|f(x)|$ is an open set and so that it has not a maximum?







share|cite|improve this question













I am studying analysis and I have had a lot of uncertainties. For instance, I cannot solve this exercise:



If $f:UrightarrowmathbbR^3$ has class $C^1$ and rank $3$ in all of the points of the open $UinmathbbR^4$, show that $|f(x)|$ do not assume maximal value for $xin U$.



(I guess this is the comand, but I'm so sorry if I did mistakes. My language and the language of the comand is Portuguese)



Well. I know that $f$ is a submersion. So, it's an open map. From here can I get the required? If I know that $f$ is an open map, have I that $|f(x)|$ is an open set and so that it has not a maximum?









share|cite|improve this question












share|cite|improve this question




share|cite|improve this question








edited Jul 17 at 0:14
























asked Jul 16 at 18:48









Na'omi

83




83











  • Your second paragraph makes no sense to me.
    – zhw.
    Jul 16 at 20:08










  • Sorry, I did a mistake and I hope now the question is correct. Thanks.
    – Na'omi
    Jul 16 at 21:52

















  • Your second paragraph makes no sense to me.
    – zhw.
    Jul 16 at 20:08










  • Sorry, I did a mistake and I hope now the question is correct. Thanks.
    – Na'omi
    Jul 16 at 21:52
















Your second paragraph makes no sense to me.
– zhw.
Jul 16 at 20:08




Your second paragraph makes no sense to me.
– zhw.
Jul 16 at 20:08












Sorry, I did a mistake and I hope now the question is correct. Thanks.
– Na'omi
Jul 16 at 21:52





Sorry, I did a mistake and I hope now the question is correct. Thanks.
– Na'omi
Jul 16 at 21:52
















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