Circle equation  TOPIC_SOLVED

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Circle equation

Postby rogermiranda00 on Wed Mar 19, 2014 1:10 pm

I have to write a polynomial equation based on this info.
Then tell what conic the equation describes.

The distance from a point (x,y) to a fixed point (-3,0) is twice the distance form the point to another fixed point (3,0).

Here is what I did.

The distance from (x,y) to (-3,0) is d1
The distance from (x,y) to (3,0) is d2
d1 = 2* d2
Using the distance formula and doing the algebra I get x^2 - 30x + 3y^2 = 0.
The correct answer is x^2 + y^2 - 10x + 9 = 0 which is a circle.

Can someone please give me a hint for this. thanks.
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Postby stapel_eliz on Wed Mar 19, 2014 1:38 pm

rogermiranda00 wrote:Using the distance formula and doing the algebra I get x^2 - 30x + 3y^2 = 0.

Please reply showing these steps, so any errors can be located and corrected. Thank you! :wink:
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Re: Circle equation  TOPIC_SOLVED

Postby rogermiranda00 on Wed Mar 19, 2014 6:55 pm

Thanks! I reworked the problem and got the right answer! I found my own mistake.
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