Show that $min M$ is unique












0












$begingroup$


Let $S$ be a subspace of a normed linear space, $X$ and $x_0in Xbackslash S$. Consider the subspace spanned by $M,$ i.e.
begin{align} M:=[Scup {x_0}]={m=x+alpha,x_0:,xin S,;text{for some};alphainBbb{R}} end{align}
I want to show that $m$ is unique.



MY TRIAL



Let $min M,$ then there exists $alphainBbb{R} $ such that $m=x+alpha,x_0.$ Suppose we have another representation, then there exists $betain Bbb{R},;betaneq alpha,$ such that $m=x+beta,x_0.$ Thus,
begin{align} x_0=0 ;text{which implies};x_0in S,;text{contradiction, since }; x_0notin S.end{align}
Please, I'm I right? If not, could you please, provide an alternative proof?










share|cite|improve this question











$endgroup$












  • $begingroup$
    I'm not 100% sure I understand the question. As I understand it, you're trying to show that, if you have $x + alpha x_0 = y + beta x_0$, where $x, y in S$, then $x = y$ and $alpha = beta$?
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:01










  • $begingroup$
    @Theo Bendit: That's true! That almost shows that I'm not correct!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:02










  • $begingroup$
    You're almost correct; instead consider $x - y = (beta - alpha)x_0$.
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:03










  • $begingroup$
    @Theo Bendit: Okay, let me try that!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:04










  • $begingroup$
    If you get, write an answer. :-)
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:05
















0












$begingroup$


Let $S$ be a subspace of a normed linear space, $X$ and $x_0in Xbackslash S$. Consider the subspace spanned by $M,$ i.e.
begin{align} M:=[Scup {x_0}]={m=x+alpha,x_0:,xin S,;text{for some};alphainBbb{R}} end{align}
I want to show that $m$ is unique.



MY TRIAL



Let $min M,$ then there exists $alphainBbb{R} $ such that $m=x+alpha,x_0.$ Suppose we have another representation, then there exists $betain Bbb{R},;betaneq alpha,$ such that $m=x+beta,x_0.$ Thus,
begin{align} x_0=0 ;text{which implies};x_0in S,;text{contradiction, since }; x_0notin S.end{align}
Please, I'm I right? If not, could you please, provide an alternative proof?










share|cite|improve this question











$endgroup$












  • $begingroup$
    I'm not 100% sure I understand the question. As I understand it, you're trying to show that, if you have $x + alpha x_0 = y + beta x_0$, where $x, y in S$, then $x = y$ and $alpha = beta$?
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:01










  • $begingroup$
    @Theo Bendit: That's true! That almost shows that I'm not correct!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:02










  • $begingroup$
    You're almost correct; instead consider $x - y = (beta - alpha)x_0$.
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:03










  • $begingroup$
    @Theo Bendit: Okay, let me try that!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:04










  • $begingroup$
    If you get, write an answer. :-)
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:05














0












0








0


1



$begingroup$


Let $S$ be a subspace of a normed linear space, $X$ and $x_0in Xbackslash S$. Consider the subspace spanned by $M,$ i.e.
begin{align} M:=[Scup {x_0}]={m=x+alpha,x_0:,xin S,;text{for some};alphainBbb{R}} end{align}
I want to show that $m$ is unique.



MY TRIAL



Let $min M,$ then there exists $alphainBbb{R} $ such that $m=x+alpha,x_0.$ Suppose we have another representation, then there exists $betain Bbb{R},;betaneq alpha,$ such that $m=x+beta,x_0.$ Thus,
begin{align} x_0=0 ;text{which implies};x_0in S,;text{contradiction, since }; x_0notin S.end{align}
Please, I'm I right? If not, could you please, provide an alternative proof?










share|cite|improve this question











$endgroup$




Let $S$ be a subspace of a normed linear space, $X$ and $x_0in Xbackslash S$. Consider the subspace spanned by $M,$ i.e.
begin{align} M:=[Scup {x_0}]={m=x+alpha,x_0:,xin S,;text{for some};alphainBbb{R}} end{align}
I want to show that $m$ is unique.



MY TRIAL



Let $min M,$ then there exists $alphainBbb{R} $ such that $m=x+alpha,x_0.$ Suppose we have another representation, then there exists $betain Bbb{R},;betaneq alpha,$ such that $m=x+beta,x_0.$ Thus,
begin{align} x_0=0 ;text{which implies};x_0in S,;text{contradiction, since }; x_0notin S.end{align}
Please, I'm I right? If not, could you please, provide an alternative proof?







linear-algebra functional-analysis analysis proof-writing proof-explanation






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 10 at 7:06







Omojola Micheal

















asked Jan 10 at 4:54









Omojola MichealOmojola Micheal

1,824324




1,824324












  • $begingroup$
    I'm not 100% sure I understand the question. As I understand it, you're trying to show that, if you have $x + alpha x_0 = y + beta x_0$, where $x, y in S$, then $x = y$ and $alpha = beta$?
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:01










  • $begingroup$
    @Theo Bendit: That's true! That almost shows that I'm not correct!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:02










  • $begingroup$
    You're almost correct; instead consider $x - y = (beta - alpha)x_0$.
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:03










  • $begingroup$
    @Theo Bendit: Okay, let me try that!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:04










  • $begingroup$
    If you get, write an answer. :-)
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:05


















  • $begingroup$
    I'm not 100% sure I understand the question. As I understand it, you're trying to show that, if you have $x + alpha x_0 = y + beta x_0$, where $x, y in S$, then $x = y$ and $alpha = beta$?
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:01










  • $begingroup$
    @Theo Bendit: That's true! That almost shows that I'm not correct!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:02










  • $begingroup$
    You're almost correct; instead consider $x - y = (beta - alpha)x_0$.
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:03










  • $begingroup$
    @Theo Bendit: Okay, let me try that!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:04










  • $begingroup$
    If you get, write an answer. :-)
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:05
















$begingroup$
I'm not 100% sure I understand the question. As I understand it, you're trying to show that, if you have $x + alpha x_0 = y + beta x_0$, where $x, y in S$, then $x = y$ and $alpha = beta$?
$endgroup$
– Theo Bendit
Jan 10 at 5:01




$begingroup$
I'm not 100% sure I understand the question. As I understand it, you're trying to show that, if you have $x + alpha x_0 = y + beta x_0$, where $x, y in S$, then $x = y$ and $alpha = beta$?
$endgroup$
– Theo Bendit
Jan 10 at 5:01












$begingroup$
@Theo Bendit: That's true! That almost shows that I'm not correct!
$endgroup$
– Omojola Micheal
Jan 10 at 5:02




$begingroup$
@Theo Bendit: That's true! That almost shows that I'm not correct!
$endgroup$
– Omojola Micheal
Jan 10 at 5:02












$begingroup$
You're almost correct; instead consider $x - y = (beta - alpha)x_0$.
$endgroup$
– Theo Bendit
Jan 10 at 5:03




$begingroup$
You're almost correct; instead consider $x - y = (beta - alpha)x_0$.
$endgroup$
– Theo Bendit
Jan 10 at 5:03












$begingroup$
@Theo Bendit: Okay, let me try that!
$endgroup$
– Omojola Micheal
Jan 10 at 5:04




$begingroup$
@Theo Bendit: Okay, let me try that!
$endgroup$
– Omojola Micheal
Jan 10 at 5:04












$begingroup$
If you get, write an answer. :-)
$endgroup$
– Theo Bendit
Jan 10 at 5:05




$begingroup$
If you get, write an answer. :-)
$endgroup$
– Theo Bendit
Jan 10 at 5:05










1 Answer
1






active

oldest

votes


















1












$begingroup$

Credits to @Theo Bendit for the hints.



Corrected:



Let $x_0in Xbackslash S$ be arbitrary. Suppose that $min M, $ then there exists $xin S;text{and};alphainBbb{R} $ such that $m=x+alpha,x_0.$ Assume there is another representation, then there exists $yin S;text{and};betain Bbb{R}$ such that $m=y+beta,x_0,$ where $xneq y$ or $alphaneqbeta$. If $xneq y$, then $beta neq alpha.$ Otherwise, if $beta neq alpha$ then $x=y$ or $xneq y.$ In both cases, $beta neq alpha$. Thus,
begin{align} left(x+alpha,x_0=y+beta,x_0right)&implies (x-y)=(beta-alpha),x_0\&implies x_0=dfrac{1}{beta-alpha}(x-y)in S,;text{where};beta-alphaneq 0;text{and};x-yin S,\&implies x_0in S,;text{since };S;text{is a subspace of a normed linear space }\&impliestext{a contradiction }end{align}
Hence, the representation $m=x+alpha x_0,;$ for $;min M$ is unique.






share|cite|improve this answer











$endgroup$









  • 1




    $begingroup$
    You should make the final implication more clear. What's wrong with $alpha - beta neq 0$? You should be able to use this assumption to conclude $x_0 in S$ (though you won't be able to conclude $x_0 = 0$).
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:17










  • $begingroup$
    @Theo Bendit: Okay, thanks for the guidiance.
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:18










  • $begingroup$
    Hint: subspaces are closed under subtraction and scalar multipliaction.
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:38










  • $begingroup$
    @Theo Bendit: Okay, thanks, once again, for the guidiance. You have my respect!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:51








  • 1




    $begingroup$
    @Theo Bendit: Thanks a lot for your time and efforts.
    $endgroup$
    – Omojola Micheal
    Jan 10 at 6:11











Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














draft saved

draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3068254%2fshow-that-m-in-m-is-unique%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









1












$begingroup$

Credits to @Theo Bendit for the hints.



Corrected:



Let $x_0in Xbackslash S$ be arbitrary. Suppose that $min M, $ then there exists $xin S;text{and};alphainBbb{R} $ such that $m=x+alpha,x_0.$ Assume there is another representation, then there exists $yin S;text{and};betain Bbb{R}$ such that $m=y+beta,x_0,$ where $xneq y$ or $alphaneqbeta$. If $xneq y$, then $beta neq alpha.$ Otherwise, if $beta neq alpha$ then $x=y$ or $xneq y.$ In both cases, $beta neq alpha$. Thus,
begin{align} left(x+alpha,x_0=y+beta,x_0right)&implies (x-y)=(beta-alpha),x_0\&implies x_0=dfrac{1}{beta-alpha}(x-y)in S,;text{where};beta-alphaneq 0;text{and};x-yin S,\&implies x_0in S,;text{since };S;text{is a subspace of a normed linear space }\&impliestext{a contradiction }end{align}
Hence, the representation $m=x+alpha x_0,;$ for $;min M$ is unique.






share|cite|improve this answer











$endgroup$









  • 1




    $begingroup$
    You should make the final implication more clear. What's wrong with $alpha - beta neq 0$? You should be able to use this assumption to conclude $x_0 in S$ (though you won't be able to conclude $x_0 = 0$).
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:17










  • $begingroup$
    @Theo Bendit: Okay, thanks for the guidiance.
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:18










  • $begingroup$
    Hint: subspaces are closed under subtraction and scalar multipliaction.
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:38










  • $begingroup$
    @Theo Bendit: Okay, thanks, once again, for the guidiance. You have my respect!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:51








  • 1




    $begingroup$
    @Theo Bendit: Thanks a lot for your time and efforts.
    $endgroup$
    – Omojola Micheal
    Jan 10 at 6:11
















1












$begingroup$

Credits to @Theo Bendit for the hints.



Corrected:



Let $x_0in Xbackslash S$ be arbitrary. Suppose that $min M, $ then there exists $xin S;text{and};alphainBbb{R} $ such that $m=x+alpha,x_0.$ Assume there is another representation, then there exists $yin S;text{and};betain Bbb{R}$ such that $m=y+beta,x_0,$ where $xneq y$ or $alphaneqbeta$. If $xneq y$, then $beta neq alpha.$ Otherwise, if $beta neq alpha$ then $x=y$ or $xneq y.$ In both cases, $beta neq alpha$. Thus,
begin{align} left(x+alpha,x_0=y+beta,x_0right)&implies (x-y)=(beta-alpha),x_0\&implies x_0=dfrac{1}{beta-alpha}(x-y)in S,;text{where};beta-alphaneq 0;text{and};x-yin S,\&implies x_0in S,;text{since };S;text{is a subspace of a normed linear space }\&impliestext{a contradiction }end{align}
Hence, the representation $m=x+alpha x_0,;$ for $;min M$ is unique.






share|cite|improve this answer











$endgroup$









  • 1




    $begingroup$
    You should make the final implication more clear. What's wrong with $alpha - beta neq 0$? You should be able to use this assumption to conclude $x_0 in S$ (though you won't be able to conclude $x_0 = 0$).
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:17










  • $begingroup$
    @Theo Bendit: Okay, thanks for the guidiance.
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:18










  • $begingroup$
    Hint: subspaces are closed under subtraction and scalar multipliaction.
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:38










  • $begingroup$
    @Theo Bendit: Okay, thanks, once again, for the guidiance. You have my respect!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:51








  • 1




    $begingroup$
    @Theo Bendit: Thanks a lot for your time and efforts.
    $endgroup$
    – Omojola Micheal
    Jan 10 at 6:11














1












1








1





$begingroup$

Credits to @Theo Bendit for the hints.



Corrected:



Let $x_0in Xbackslash S$ be arbitrary. Suppose that $min M, $ then there exists $xin S;text{and};alphainBbb{R} $ such that $m=x+alpha,x_0.$ Assume there is another representation, then there exists $yin S;text{and};betain Bbb{R}$ such that $m=y+beta,x_0,$ where $xneq y$ or $alphaneqbeta$. If $xneq y$, then $beta neq alpha.$ Otherwise, if $beta neq alpha$ then $x=y$ or $xneq y.$ In both cases, $beta neq alpha$. Thus,
begin{align} left(x+alpha,x_0=y+beta,x_0right)&implies (x-y)=(beta-alpha),x_0\&implies x_0=dfrac{1}{beta-alpha}(x-y)in S,;text{where};beta-alphaneq 0;text{and};x-yin S,\&implies x_0in S,;text{since };S;text{is a subspace of a normed linear space }\&impliestext{a contradiction }end{align}
Hence, the representation $m=x+alpha x_0,;$ for $;min M$ is unique.






share|cite|improve this answer











$endgroup$



Credits to @Theo Bendit for the hints.



Corrected:



Let $x_0in Xbackslash S$ be arbitrary. Suppose that $min M, $ then there exists $xin S;text{and};alphainBbb{R} $ such that $m=x+alpha,x_0.$ Assume there is another representation, then there exists $yin S;text{and};betain Bbb{R}$ such that $m=y+beta,x_0,$ where $xneq y$ or $alphaneqbeta$. If $xneq y$, then $beta neq alpha.$ Otherwise, if $beta neq alpha$ then $x=y$ or $xneq y.$ In both cases, $beta neq alpha$. Thus,
begin{align} left(x+alpha,x_0=y+beta,x_0right)&implies (x-y)=(beta-alpha),x_0\&implies x_0=dfrac{1}{beta-alpha}(x-y)in S,;text{where};beta-alphaneq 0;text{and};x-yin S,\&implies x_0in S,;text{since };S;text{is a subspace of a normed linear space }\&impliestext{a contradiction }end{align}
Hence, the representation $m=x+alpha x_0,;$ for $;min M$ is unique.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Jan 10 at 6:44

























answered Jan 10 at 5:14









Omojola MichealOmojola Micheal

1,824324




1,824324








  • 1




    $begingroup$
    You should make the final implication more clear. What's wrong with $alpha - beta neq 0$? You should be able to use this assumption to conclude $x_0 in S$ (though you won't be able to conclude $x_0 = 0$).
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:17










  • $begingroup$
    @Theo Bendit: Okay, thanks for the guidiance.
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:18










  • $begingroup$
    Hint: subspaces are closed under subtraction and scalar multipliaction.
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:38










  • $begingroup$
    @Theo Bendit: Okay, thanks, once again, for the guidiance. You have my respect!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:51








  • 1




    $begingroup$
    @Theo Bendit: Thanks a lot for your time and efforts.
    $endgroup$
    – Omojola Micheal
    Jan 10 at 6:11














  • 1




    $begingroup$
    You should make the final implication more clear. What's wrong with $alpha - beta neq 0$? You should be able to use this assumption to conclude $x_0 in S$ (though you won't be able to conclude $x_0 = 0$).
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:17










  • $begingroup$
    @Theo Bendit: Okay, thanks for the guidiance.
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:18










  • $begingroup$
    Hint: subspaces are closed under subtraction and scalar multipliaction.
    $endgroup$
    – Theo Bendit
    Jan 10 at 5:38










  • $begingroup$
    @Theo Bendit: Okay, thanks, once again, for the guidiance. You have my respect!
    $endgroup$
    – Omojola Micheal
    Jan 10 at 5:51








  • 1




    $begingroup$
    @Theo Bendit: Thanks a lot for your time and efforts.
    $endgroup$
    – Omojola Micheal
    Jan 10 at 6:11








1




1




$begingroup$
You should make the final implication more clear. What's wrong with $alpha - beta neq 0$? You should be able to use this assumption to conclude $x_0 in S$ (though you won't be able to conclude $x_0 = 0$).
$endgroup$
– Theo Bendit
Jan 10 at 5:17




$begingroup$
You should make the final implication more clear. What's wrong with $alpha - beta neq 0$? You should be able to use this assumption to conclude $x_0 in S$ (though you won't be able to conclude $x_0 = 0$).
$endgroup$
– Theo Bendit
Jan 10 at 5:17












$begingroup$
@Theo Bendit: Okay, thanks for the guidiance.
$endgroup$
– Omojola Micheal
Jan 10 at 5:18




$begingroup$
@Theo Bendit: Okay, thanks for the guidiance.
$endgroup$
– Omojola Micheal
Jan 10 at 5:18












$begingroup$
Hint: subspaces are closed under subtraction and scalar multipliaction.
$endgroup$
– Theo Bendit
Jan 10 at 5:38




$begingroup$
Hint: subspaces are closed under subtraction and scalar multipliaction.
$endgroup$
– Theo Bendit
Jan 10 at 5:38












$begingroup$
@Theo Bendit: Okay, thanks, once again, for the guidiance. You have my respect!
$endgroup$
– Omojola Micheal
Jan 10 at 5:51






$begingroup$
@Theo Bendit: Okay, thanks, once again, for the guidiance. You have my respect!
$endgroup$
– Omojola Micheal
Jan 10 at 5:51






1




1




$begingroup$
@Theo Bendit: Thanks a lot for your time and efforts.
$endgroup$
– Omojola Micheal
Jan 10 at 6:11




$begingroup$
@Theo Bendit: Thanks a lot for your time and efforts.
$endgroup$
– Omojola Micheal
Jan 10 at 6:11


















draft saved

draft discarded




















































Thanks for contributing an answer to Mathematics Stack Exchange!


  • Please be sure to answer the question. Provide details and share your research!

But avoid



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


Use MathJax to format equations. MathJax reference.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3068254%2fshow-that-m-in-m-is-unique%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

Mario Kart Wii

The Binding of Isaac: Rebirth/Afterbirth

What does “Dominus providebit” mean?