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Circle Geometry help

I've been stuck on the following question and am unsure of how to complete it.

The circle C has equation X^2+y^2+4x-2y-11=0
Find:
a) The co-ordinates of the centre of the circle
b)The radius
c)the co-ordinates of the points where C crosses the y-axis, giving your answers in simplified surd form.

So far i've managed both a) and b) getting (-2,1) for the centre and 4 for the radius. However i haven't a clue how to begin C and any help would be greatly appreciated.
Original post by randomhobo
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When it crosses the y-axis, what's the value of the x co-ordinate? Can you take it from there.
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randomhobo
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Original post by ghostwalker
When it crosses the y-axis, what's the value of the x co-ordinate? Can you take it from there.


The thing is i don't know where it crosses the X-axis, i have to simply find where it crosses the y-axis.
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jarasta
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Original post by randomhobo
The thing is i don't know where it crosses the X-axis, i have to simply find where it crosses the y-axis.


Sub x=0 then solve for y because whereever it will cross you can guarantee it will cross at (0,y)

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randomhobo
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Original post by jarasta
Sub x=0 then solve for y because whereever it will cross you can guarantee it will cross at (0,y)

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Thank's for the help. I believe i've gotten the correct answer as y=+/- 2 root 3, -1

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