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two answers but i got only one

 
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mun
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PostPosted: Sat, 7 Nov 2009 18:09:46 UTC    Post subject: two answers but i got only one Reply with quote

Find the direction in which a straight line must be drawn through the point (–1, 2)so that its point of intersection with the line be at a distance of 3 units from this point.

my work
i solved this and got the answer a line parallel to x axis .
first i find the equation of required line by taking its slope as m .i e [y-2=m(x+1)]. then i found the point of intersection of y-2=m(x+1) with the line x + y = 4 . after applying distance formula i got the answer as m=0 i.e a line parallel to x axis which is correct if we do calculation wise . but there is another answer which is a line parallel to y axis and i have checked this answer is geometrically correct.why analytically second answer is not coming.where is the fallacy.
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robbwrr
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PostPosted: Sat, 7 Nov 2009 20:39:15 UTC    Post subject: Reply with quote

Let (t,4-t) be the point on line x+y=4 then

produces two solutions etc.
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mun
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PostPosted: Sun, 8 Nov 2009 07:10:07 UTC    Post subject: reply Reply with quote

robbwrr wrote:
Let (t,4-t) be the point on line x+y=4 then

produces two solutions etc.

Good morning sir
thanks sir
sir why the slope method fail here.
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Shadow
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PostPosted: Sun, 8 Nov 2009 19:02:31 UTC    Post subject: Re: reply Reply with quote

mun wrote:
robbwrr wrote:
Let (t,4-t) be the point on line x+y=4 then

produces two solutions etc.

Good morning sir
thanks sir
sir why the slope method fail here.


What is the slope method?
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outermeasure
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PostPosted: Mon, 9 Nov 2009 00:32:24 UTC    Post subject: Re: reply Reply with quote

mun wrote:
robbwrr wrote:
Let (t,4-t) be the point on line x+y=4 then

produces two solutions etc.

Good morning sir
thanks sir
sir why the slope method fail here.


Because you assumed the slope is finite. (Indeed, you would have cancelled m^2 from both side....)
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