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core1 - point of intersection question

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    Find the co-ordinates of the point of intersection between the line y=5-x and the curve xy=-4.
    so far , i substituted y=5-x into the equation xy=-4 to get: -x^2+5x+4=0
    then i completed the square since i couldnt factorise that. and the x cordinate from the completing the square was 5/2. what do i do after this to find the points of intersection?
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    (Original post by Chelsea12345)
    Find the co-ordinates of the point of intersection between the line y=5-x and the curve xy=-4.
    so far , i substituted y=5-x into the equation xy=-4 to get: -x^2+5x+4=0
    then i completed the square since i couldnt factorise that. and the x cordinate from the completing the square was 5/2. what do i do after this to find the points of intersection?
    Firstly, there are two point of intersection so you need 2 x-coordinates that you get from solving the quadratic.

    Secondly, you must've completed the square correctly, but you did not solve for x.

    Thirdly, once you have the two x-coordinates, subtitute them into the line equation to get your y-values.
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    (Original post by Chelsea12345)
    Find the co-ordinates of the point of intersection between the line y=5-x and the curve xy=-4.
    so far , i substituted y=5-x into the equation xy=-4 to get: -x^2+5x+4=0
    then i completed the square since i couldnt factorise that. and the x cordinate from the completing the square was 5/2. what do i do after this to find the points of intersection?
    You should obtain the quadratic  x^2-5x-4=0 .
    You should find the x coordinates and then sub these x values to find y to find the coordinates a of intersection.
 
 
 
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