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Math Help - Quadratic graph; solving equations.

  1. #1
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    Quadratic graph; solving equations.

    Hi, I hope someone will help me! I've got a graph of x2+3x=8 (quadratic). By drawing a suitable straigt line on the graph, I need to solve the equation: x2+2x-4=0 (quadratic) How do I draw the second graph without solving the equation first?
    Thank you for your help!
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  2. #2
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    Quote Originally Posted by vanklik View Post
    Hi, I hope someone will help me! I've got a graph of x2+3x=8 (quadratic). By drawing a suitable straigt line on the graph, I need to solve the equation: x2+2x-4=0 (quadratic) How do I draw the second graph without solving the equation first?
    Thank you for your help!
    Hi vanklik,

    x^2+2x-4=(x^2+3x-8)-(x-4)

    Therefore you can solve x^2+2x-4=0 by solving (x^2+3x-8)-(x-4)=0

    In other words, by finding where the line x-4 crosses the curve x^2+3x-8
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