$u, v, n$ are vectors in $mathbbR^2$, show that $(u-v)$ is $perp n$

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Let $l : Ax+By+C= 0$ be a straight line. Let $overrightarrowu=u_1overrightarrowi+u_2overrightarrowj$ and $overrightarrowv=v_1overrightarrowi+v_2overrightarrowj$ be two points on $l$ with $overrightarrowu-overrightarrowvneq 0$, $overrightarrown=Aoverrightarrowi+Boverrightarrowj$. Show that$(overrightarrowu-overrightarrowv) perp overrightarrown$.







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  • What have you done so far? Tell us where you are stuck.
    – Kavi Rama Murthy
    Jul 25 at 8:28










  • n should be on the line l, shouldn't it? that means it's impossible for l to perpendicular to n?
    – Astrid L
    Jul 25 at 8:32










  • It is not on the line; it is perpendicular to the line.
    – Kavi Rama Murthy
    Jul 25 at 8:34










  • @KaviRamaMurthy but as you can see, n=Ai+Bj. It's at least parallel to l...?
    – Astrid L
    Jul 25 at 8:36














up vote
-1
down vote

favorite












Let $l : Ax+By+C= 0$ be a straight line. Let $overrightarrowu=u_1overrightarrowi+u_2overrightarrowj$ and $overrightarrowv=v_1overrightarrowi+v_2overrightarrowj$ be two points on $l$ with $overrightarrowu-overrightarrowvneq 0$, $overrightarrown=Aoverrightarrowi+Boverrightarrowj$. Show that$(overrightarrowu-overrightarrowv) perp overrightarrown$.







share|cite|improve this question





















  • What have you done so far? Tell us where you are stuck.
    – Kavi Rama Murthy
    Jul 25 at 8:28










  • n should be on the line l, shouldn't it? that means it's impossible for l to perpendicular to n?
    – Astrid L
    Jul 25 at 8:32










  • It is not on the line; it is perpendicular to the line.
    – Kavi Rama Murthy
    Jul 25 at 8:34










  • @KaviRamaMurthy but as you can see, n=Ai+Bj. It's at least parallel to l...?
    – Astrid L
    Jul 25 at 8:36












up vote
-1
down vote

favorite









up vote
-1
down vote

favorite











Let $l : Ax+By+C= 0$ be a straight line. Let $overrightarrowu=u_1overrightarrowi+u_2overrightarrowj$ and $overrightarrowv=v_1overrightarrowi+v_2overrightarrowj$ be two points on $l$ with $overrightarrowu-overrightarrowvneq 0$, $overrightarrown=Aoverrightarrowi+Boverrightarrowj$. Show that$(overrightarrowu-overrightarrowv) perp overrightarrown$.







share|cite|improve this question













Let $l : Ax+By+C= 0$ be a straight line. Let $overrightarrowu=u_1overrightarrowi+u_2overrightarrowj$ and $overrightarrowv=v_1overrightarrowi+v_2overrightarrowj$ be two points on $l$ with $overrightarrowu-overrightarrowvneq 0$, $overrightarrown=Aoverrightarrowi+Boverrightarrowj$. Show that$(overrightarrowu-overrightarrowv) perp overrightarrown$.









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share|cite|improve this question




share|cite|improve this question








edited Jul 25 at 8:30









Jack J.

3661317




3661317









asked Jul 25 at 8:24









Astrid L

23




23











  • What have you done so far? Tell us where you are stuck.
    – Kavi Rama Murthy
    Jul 25 at 8:28










  • n should be on the line l, shouldn't it? that means it's impossible for l to perpendicular to n?
    – Astrid L
    Jul 25 at 8:32










  • It is not on the line; it is perpendicular to the line.
    – Kavi Rama Murthy
    Jul 25 at 8:34










  • @KaviRamaMurthy but as you can see, n=Ai+Bj. It's at least parallel to l...?
    – Astrid L
    Jul 25 at 8:36
















  • What have you done so far? Tell us where you are stuck.
    – Kavi Rama Murthy
    Jul 25 at 8:28










  • n should be on the line l, shouldn't it? that means it's impossible for l to perpendicular to n?
    – Astrid L
    Jul 25 at 8:32










  • It is not on the line; it is perpendicular to the line.
    – Kavi Rama Murthy
    Jul 25 at 8:34










  • @KaviRamaMurthy but as you can see, n=Ai+Bj. It's at least parallel to l...?
    – Astrid L
    Jul 25 at 8:36















What have you done so far? Tell us where you are stuck.
– Kavi Rama Murthy
Jul 25 at 8:28




What have you done so far? Tell us where you are stuck.
– Kavi Rama Murthy
Jul 25 at 8:28












n should be on the line l, shouldn't it? that means it's impossible for l to perpendicular to n?
– Astrid L
Jul 25 at 8:32




n should be on the line l, shouldn't it? that means it's impossible for l to perpendicular to n?
– Astrid L
Jul 25 at 8:32












It is not on the line; it is perpendicular to the line.
– Kavi Rama Murthy
Jul 25 at 8:34




It is not on the line; it is perpendicular to the line.
– Kavi Rama Murthy
Jul 25 at 8:34












@KaviRamaMurthy but as you can see, n=Ai+Bj. It's at least parallel to l...?
– Astrid L
Jul 25 at 8:36




@KaviRamaMurthy but as you can see, n=Ai+Bj. It's at least parallel to l...?
– Astrid L
Jul 25 at 8:36










1 Answer
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Show that the scalar product $(overrightarrowu-overrightarrowv) cdot overrightarrown=0$.



Use that $overrightarrowu cdot overrightarrown= -C$ and $overrightarrowv cdot overrightarrown= -C$.






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  • What is the second line doing?
    – Astrid L
    Jul 25 at 12:02










  • $overrightarrowu$ is on $l$, hence $Au_1+Bu_2+C=0$.
    – Fred
    Jul 26 at 5:57










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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
0
down vote













Show that the scalar product $(overrightarrowu-overrightarrowv) cdot overrightarrown=0$.



Use that $overrightarrowu cdot overrightarrown= -C$ and $overrightarrowv cdot overrightarrown= -C$.






share|cite|improve this answer





















  • What is the second line doing?
    – Astrid L
    Jul 25 at 12:02










  • $overrightarrowu$ is on $l$, hence $Au_1+Bu_2+C=0$.
    – Fred
    Jul 26 at 5:57














up vote
0
down vote













Show that the scalar product $(overrightarrowu-overrightarrowv) cdot overrightarrown=0$.



Use that $overrightarrowu cdot overrightarrown= -C$ and $overrightarrowv cdot overrightarrown= -C$.






share|cite|improve this answer





















  • What is the second line doing?
    – Astrid L
    Jul 25 at 12:02










  • $overrightarrowu$ is on $l$, hence $Au_1+Bu_2+C=0$.
    – Fred
    Jul 26 at 5:57












up vote
0
down vote










up vote
0
down vote









Show that the scalar product $(overrightarrowu-overrightarrowv) cdot overrightarrown=0$.



Use that $overrightarrowu cdot overrightarrown= -C$ and $overrightarrowv cdot overrightarrown= -C$.






share|cite|improve this answer













Show that the scalar product $(overrightarrowu-overrightarrowv) cdot overrightarrown=0$.



Use that $overrightarrowu cdot overrightarrown= -C$ and $overrightarrowv cdot overrightarrown= -C$.







share|cite|improve this answer













share|cite|improve this answer



share|cite|improve this answer











answered Jul 25 at 8:29









Fred

37.2k1237




37.2k1237











  • What is the second line doing?
    – Astrid L
    Jul 25 at 12:02










  • $overrightarrowu$ is on $l$, hence $Au_1+Bu_2+C=0$.
    – Fred
    Jul 26 at 5:57
















  • What is the second line doing?
    – Astrid L
    Jul 25 at 12:02










  • $overrightarrowu$ is on $l$, hence $Au_1+Bu_2+C=0$.
    – Fred
    Jul 26 at 5:57















What is the second line doing?
– Astrid L
Jul 25 at 12:02




What is the second line doing?
– Astrid L
Jul 25 at 12:02












$overrightarrowu$ is on $l$, hence $Au_1+Bu_2+C=0$.
– Fred
Jul 26 at 5:57




$overrightarrowu$ is on $l$, hence $Au_1+Bu_2+C=0$.
– Fred
Jul 26 at 5:57












 

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