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Math Help - I need to plot these Systems of Inequalities onto a graph. Help!?

  1. #1
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    I need to plot these Systems of Inequalities onto a graph. Help!?

    How can I find the coordinates to these so I can graph the lines.
    y >= 2x-3
    y < -4x-5

    There should be two lines, right? I need help finding the coordinates for each of the lines and then how I need to shade them. Left side or right side? No idea where to start. I'm a complete idiot when it comes to algebra.
    Can someone please help me out here?
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  2. #2
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    Quote Originally Posted by eraser851 View Post
    How can I find the coordinates to these so I can graph the lines.
    y >= 2x-3
    y < -4x-5

    There should be two lines, right? I need help finding the coordinates for each of the lines and then how I need to shade them. Left side or right side? No idea where to start. I'm a complete idiot when it comes to algebra.
    Can someone please help me out here?
    When graphing them, treat the inequalities as equalities like so:

    y=2x-3
    y=-4x-5

    Now, graph the lines, and look back at your original inequalities. The first inequality is the entire region above and AT the line y=2x-3. The second region is the entire region below the line y=-4x-5. The subspace region where both of these areas intersect is what you should leave as shaded in your graph. That region of x-values satisfies both equations.
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  3. #3
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    Okay, correct me if I'm wrong.

    y >= 2x-3 would have coordinates at (-2,-7) and oh lets say (3,3)

    y < -4x-5 would have coordinates at (1,-9) and say (-2,3)


    Would this be right?

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    Quote Originally Posted by eraser851 View Post
    Okay, correct me if I'm wrong.

    y >= 2x-3 would have coordinates at (-2,-7) and oh lets say (3,3)

    y < -4x-5 would have coordinates at (1,-9) and say (-2,3)


    Would this be right?

    Close.... y<-4x-5 would be the region to the left of the line.
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  5. #5
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    Alright, now I'm stuck on a new one.
    9x + 7y > -21

    Since the 'y' is in the middle, how can I make a 'y=' formula?
    And how would I know which side to shade on? Left or right?
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  6. #6
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    Quote Originally Posted by eraser851 View Post
    Alright, now I'm stuck on a new one.
    9x + 7y > -21

    Since the 'y' is in the middle, how can I make a 'y=' formula?
    And how would I know which side to shade on? Left or right?
    9x+7y > -21

    7y > -21 - 9x

    y > -3 -\frac{9}{7}x

    Shade to the right of the line y = -3 -\frac{9}{7}x
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