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Math Help - Intersection of curves

  1. #1
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    Intersection of curves

    The line y=2x- 3 intersects the curve y=x^2+x-15 at the points

    (a)(3,3)and(4,5)
    (b)(-3,-9)and(4,5)
    (c)(3,3)and(-4,-11)
    (d)(-3,-9)and(-4,-11).
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by bobby77
    The line y=2x- 3 intersects the curve y=x^2+x-15 at the points

    (a)(3,3)and(4,5)
    (b)(-3,-9)and(4,5)
    (c)(3,3)and(-4,-11)
    (d)(-3,-9)and(-4,-11).
    At a point of intersection:

    <br />
2x-3=x^2+x-15<br />
,

    so:

    <br />
x^2-x-12=0<br />

    Now trying the candidates for x, we find that , x=-3 satisfies
    this equation as does x=4, so (b) must be the answer (assuming the
    y's are OK which I suppose we can).

    RonL
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