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    Find the equation of the circle with centre(4,0) and radius 3,giving your answer in multiplied out term.
    The straight line y= kx, where k is a constant,meets the circle in part(i).
    (ii) Show that the x-co-ordinates of the points of intersection are given by the equation: (k^2+1)x^2 - 8x + 7 = 0.
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    (X-*)^2 + (y+*)^2 = r^2
    Substitute the values, then expand it and substitute y for kx and expand again if necessary
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    (Original post by zayn008)
    (X-*)^2 + (y+*)^2 = r^2
    Substitute the values, then expand it and substitute y for kx and expand again if necessary
    If i substitute y for kx i get (x-4)^2 + (kx)^2 = 9
    If i expand this and put everything to one side, i get x^2 + y^2 - 8y + 7 + k^2x^2 = 0.
    Do i put this into the brackets again to get the answer they want??
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    (Original post by Chelsea12345)
    If i substitute y for kx i get (x-4)^2 + (kx)^2 = 9
    If i expand this and put everything to one side, i get x^2 + y^2 - 8y + 7 + k^2x^2 = 0.
    Do i put this into the brackets again to get the answer they want??
    yep! It should be -8x not -8y, simply factor out x^2 and you've got the answer they're looking for
 
 
 
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