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Thread: Irrasjonale likninger (don't know what it is in English)

  1. #1 Irrasjonale likninger (don't know what it is in English) 
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    Example:

    x = √3x+7-1

    x+1 = √3x+7

    (x+1)² = (√3x+7)²

    x²+2x+1 = 3x+7

    Question: Why +2x

    x²-6-x = 0

    Question: Why -6-x?

    x = -2 OR x = 3

    Question: How can you see the answer will be -2 or 3?


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  3. #2  
    Forum Freshman sara8's Avatar
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    to expand the squared bracket like your example (x+1)^2 you square the x and then the number(1) then you multiply 1 by x by 2 (the power above the square) about your second question you move the l.h.s to the R.H.S with an opposite sign it will be x^2 +2x+1-3x-7=0 this is to be put in the form of the quadratic equation then you the equation becomes x^2-6x-1=0 this is to be able to find the roots of the quadrtic equation by the quadratic formula or by factorizing .I hope this helps .

    Sara,


    The things that hurt instruct
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  4. #3  
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    Now I understand why I couldn't figure it out. I'm taking math and had forgotten all about it, so I'm starting from scratch. It's been many years. Thanks for reply though.
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