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Math Help - Quadratic Inequalities.

  1. #1
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    Quadratic Inequalities.

    I do NOT understand how to do this. Can someone explain in full detail/step by step how to do it? Which points in the end would I graph? (for each problem)

    1) y > -x^2 -10x

    2) y< 4x^2+8x+4

    3) y>x^2-3x-18
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  2. #2
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    Quote Originally Posted by SpaceGhost View Post

    1) y > -x^2 -10x
    y > -x^2 -10x \implies y> -x(x+10)

    Solving gives us x = 0,-10 which serve as the x-axis intercepts for the inverted parabola. Graph the parabola and you have two reigions on your plane, we now have to decide which region is required.

    So choose a point anywhere i.e. (-5,0) and substitute into the equation.

    If this statement is correct then this point falls in the required region, otherwise if false, reject this region and choose the other.

    0 > -(-5)^2 -10(-5) \implies 0 > -25+50 which is false so reject this region.
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  3. #3
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    Sorry I'm still a little confused. Which is the vertex? And do I graph: (10,0 and -10,-0) or (0,0 and -10, 0)
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  4. #4
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    Grpah these two points and the parabola that passes through it.

    Quote Originally Posted by SpaceGhost View Post
    (0,0 and -10, 0)
    The vertex is not required.
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  5. #5
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    I need more help with these. :S I need to have 5 ordered pairs for each.

    I need to find the vertex, all x-intercepts, y-intercepts, and 2 "partnered pairs"
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