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Math Help - Question on quadratic and linear equation/graph

  1. #1
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    Question on quadratic and linear equation/graph



    Additional Information: The curve of y=(4-x)(x+5) cuts the x-axis at A and B. A straight line cuts the curve at A and at C. The x-coordinate of C is 2. Find
    (a) the coordinates of point C,
    (b) the equation of line AC,
    (c) the area of Triangle ABC

    I am stuck at the (a) part. I can't find a solution to get the "y" of point C. I don't see any clue too. What should I do to get "y" of point C?
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  2. #2
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    Re: Question on quadratic and linear equation/graph

    Point C is on the curve of equation y = (4-x)(x+5) so as you know the x co-ordinate you can simply sub it into the equation of the curve to find the y co-ordinate.
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  3. #3
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    Re: Question on quadratic and linear equation/graph

    The y co-ordinate of Point C is

    y=(4-x)(x+5)=f(2)

    when x=2

    as C is on both the line and curve.
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  4. #4
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    Re: Question on quadratic and linear equation/graph

    Quote Originally Posted by Archie Meade View Post
    The y co-ordinate of Point C is

    y=(4-x)(x+5)=f(2)

    when x=2

    as C is on both the line and curve.
    Quote Originally Posted by Ross137 View Post
    Point C is on the curve of equation y = (4-x)(x+5) so as you know the x co-ordinate you can simply sub it into the equation of the curve to find the y co-ordinate.
    Thanks, sorry for the late reply, I got it. =)
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