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    1) I got the answer fairly easily , which is
    x^2 + y^2 -4x - 2y - 95 =0

    2) But for number 2, I sub in the x value of 5 and the y value of k to get :
    25 + k^2 -20 - 2k - 95 =0 , which can be rearranged to k^2 - 2k - 90 = 0

    I find it difficult though to use the quadratic formula. I get until 2k +/- root 2k^2 +360k over 2k and dont know what to do next.

    3) How can you tell if it lies inside/ out ?
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    When you use the quadratic formula, you don't include the k's and k^2's - you just need to know how many there are. So the equation would be (2 +/- sqrt(2^2+4*90))/2, which comes out to 1 +/- sqrt(91).

    As for the third part, I would use pythagoras to find out the distance from the centre to (-3,9). If it's less than the radius then it's inside the circle, if not it's outside.
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    (Original post by Arbolus)
    When you use the quadratic formula, you don't include the k's and k^2's - you just need to know how many there are. So the equation would be (2 +/- sqrt(2^2+4*90))/2, which comes out to 1 +/- sqrt(91).

    As for the third part, I would use pythagoras to find out the distance from the centre to (-3,9). If it's less than the radius then it's inside the circle, if not it's outside.

    Oh yh, I didn't realise that the letter k takes the place of x.

    Edit: I'm now stuck on this part . I end up with 2+/- root 4 + 360 over 2 . Cancel out the 2 from the bottom to give:
    1+/- root182
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    (Original post by Gelato)
    Oh yh, I didn't realise that the letter k takes the place of x.

    Edit: I'm now stuck on this part . I end up with 2+/- root 4 + 360 over 2 . Cancel out the 2 from the bottom to give:
    1+/- root182
    To simplify a surd you need to take out the largest square factor you can. So:

    root(364) = root(4*91) = root(4)*root(91) = 2*root(91).
 
 
 
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