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Analytical Geometry

Blazing goIITian

Joined:	22 Jan 2007
Post:	2039

25 Feb 2007 21:56:35 IST

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920

circles and lines

None

Let L1 be a straight line passing through the origin and L2 be the straight line x+y=1.If the intercepts made by circle x2+y2-x+3y=0 on L1andL2 be equal ,then which of the following may represent L1?(a) x+y=0(b) x-y=0(c) x+7y=0(d) x-7y=0[ans: (b),(c)]

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Comments (4)

faith

Hot goIITian

Joined: 29 Jan 2007

Posts: 114

25 Feb 2007 22:56:46 IST

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this type of ques r done faster if d options r given a view over the req conditions.
btw, the way of solving is first to say y=1-x for L2 , put it in circle, get diff. of roots, for y, and then for x. now , the intercept, then consider y=mx as the req line and get intercept, n equate with the calculated one 2 get 2 val. for m.

Aashimi Bhatia

New kid on the Block

Joined: 25 Feb 2007

Posts: 20

25 Feb 2007 23:11:34 IST

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no need 2 even find da intercept... since da intercepts r supposed 2 b equal... simply equate da distances of da lines 4m da centre of da circle (taking da required line 2 b y=mx)... u will get a quadratic in m, solve it n get da answer

vishak p

Blazing goIITian

Joined: 9 Feb 2007

Posts: 1347

25 Feb 2007 23:15:01 IST

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yup , ashi's right !!!

puneet

Forum Expert

Joined: 19 Oct 2006

Posts: 1966

26 Feb 2007 22:05:23 IST

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hiiiiii

I just solved the way ashi suggested, and i am getting the correct answer. It is a very good approach i think.

Neeraj, u are clear with the approach na ???

Tell me if i need to do the calculations, though they are very simple.

cheers

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