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 Post subject: For what values of a and b are these two vectors collinear (Posted: Mon, 20 Feb 2012 06:46:37 UTC

Joined: Mon, 20 Feb 2012 06:45:27 UTC
Posts: 6
I'd like to know what the steps. I don't really care about the answer.

t = (3a -4b +5, 5b -2a -8)
v = (-3, 4)

t and v are vectors

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 Post subject: Re: For what values of a and b are these two vectors collinePosted: Mon, 20 Feb 2012 10:10:47 UTC
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wholegrain wrote:
I'd like to know what the steps. I don't really care about the answer.

t = (3a -4b +5, 5b -2a -8)
v = (-3, 4)

t and v are vectors

If and are collinear, then , so ...

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 Post subject: Re: For what values of a and b are these two vectors collinePosted: Mon, 20 Feb 2012 14:54:16 UTC

Joined: Mon, 20 Feb 2012 06:45:27 UTC
Posts: 6
The teacher gave the answer, but I have no idea what he did.

Basically, he wrote 6a -b -4 = 0

then he isolated b, which gives:

b = 6a -4

then he somehow came with

the answer, which is, like I said:

t = 7(a-1)(-3,4) or 7(a-1)vector z.

I have no idea what the teacher did.

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 Post subject: Re: For what values of a and b are these two vectors collinePosted: Mon, 20 Feb 2012 16:36:51 UTC
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Posts: 990
wholegrain wrote:
The teacher gave the answer, but I have no idea what he did.

Basically, he wrote 6a -b -4 = 0

then he isolated b, which gives:

b = 6a -4

then he somehow came with

the answer, which is, like I said:

t = 7(a-1)(-3,4) or 7(a-1)vector z.

I have no idea what the teacher did.

I would just use Outermeasure's ratio argument...

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"Mathematicians are like lovers. Grant a mathematician the least principle, and he will draw from it a consequence which you must also grant him, and from this consequence another." Bernard Le Bovier Fontenelle (1657-1757)

"In great mathematics there is a very high degree of unexpectedness, combined with inevitability and economy."
G.H. Hardy (1877-1947)

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 Post subject: Re: For what values of a and b are these two vectors collinePosted: Mon, 20 Feb 2012 17:57:44 UTC

Joined: Mon, 20 Feb 2012 06:45:27 UTC
Posts: 6

what's that?

Can you explain how he did it?

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 Post subject: Re: For what values of a and b are these two vectors collinePosted: Mon, 20 Feb 2012 18:00:13 UTC
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Joined: Wed, 30 Mar 2005 04:25:14 UTC
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wholegrain wrote:

what's that?

Can you explain how he did it?

No, outermeasure is not a person, it's one of our users who responded to you. Did you read his post? It describes exactly how to do this problem.

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 Post subject: Re: For what values of a and b are these two vectors collinePosted: Mon, 20 Feb 2012 18:30:35 UTC
 S.O.S. Oldtimer

Joined: Sat, 16 Aug 2008 04:47:19 UTC
Posts: 208
Or you can do something like so...

Get only on the RHS, set equations equal to each other find in terms of .

plug that back into one of the original equations to get in terms of .

This might be similar to what your teacher did.

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 Post subject: Re: For what values of a and b are these two vectors collinePosted: Mon, 20 Feb 2012 21:07:07 UTC

Joined: Mon, 20 Feb 2012 06:45:27 UTC
Posts: 6
wholegrain wrote:

what's that?

Can you explain how he did it?

No, outermeasure is not a person, it's one of our users who responded to you. Did you read his post? It describes exactly how to do this problem.

I am asking because obviously I have never heard of it.

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 Post subject: Re: For what values of a and b are these two vectors collinePosted: Mon, 20 Feb 2012 21:41:03 UTC

Joined: Mon, 20 Feb 2012 06:45:27 UTC
Posts: 6
the question states for what value of a and b, but how come the answer is 7(a-1)?

so b = 0 and a = R?

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 Post subject: Re: For what values of a and b are these two vectors collinePosted: Mon, 20 Feb 2012 22:21:43 UTC
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Joined: Wed, 30 Mar 2005 04:25:14 UTC
Posts: 12098
Location: Austin, TX
wholegrain wrote:
wholegrain wrote:

what's that?

Can you explain how he did it?

No, outermeasure is not a person, it's one of our users who responded to you. Did you read his post? It describes exactly how to do this problem.

I am asking because obviously I have never heard of it.

Ah, then you shouldn't have included the google search, it made it seem like you thought this was some famous argument with a special name you had searched for but had been unable to find.

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