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Math Help - circles help please

  1. #1
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    circles help please

    x^2-12x+y^2+4y+15=0

    a) specifies a circle. find its centre and radius.


    b) Find the coordinates of any points at which the circle in part (a) intersects line y=x-9
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  2. #2
    Like a stone-audioslave ADARSH's Avatar
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    Quote Originally Posted by toplad View Post
    x^2-12x+y^2+4y+15=0

    a) specifies a circle. find its centre and radius.


    b) Find the coordinates of any points at which the circle in part (a) intersects line y=x-9
    a)
     <br />
x^2-12x+36 + y^2 +4y+4 -25=0<br />

     <br />
(x-6)^2+(y+2)^2=5^2<br />

    hence the coordinates of centre are (6,-2)
    and radius is 5
    b)
    -put the value of y from line's equation into that of circle

    -solve the quadratic equation that follows

    -for the values of x you get find y and the corresponding pairs
    are point of intersection

    Now try this yourself now
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