Solve For x

Discussion in 'Other Pre-University Math' started by nycmathguy, Feb 6, 2022.

  1. nycmathguy

    nycmathguy

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    David Cohen questions just for fun.
    Enjoy.

    IMG_20220205_215257.jpg
     
    nycmathguy, Feb 6, 2022
    #1
  2. nycmathguy

    MathLover1

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    x+12/x=(sqrt(x)-sqrt(12/x))^2+2sqrt(12)

    x+12/x=(sqrt(x))^2-2sqrt(x)sqrt(12/x)+(sqrt(12/x))^2+2sqrt(12)

    x+12/x=x-2sqrt(x)sqrt(12/x)+12/x+2sqrt(12).......simplify

    0=-2sqrt(x)sqrt(12/x)+2sqrt(12)

    0=-2(sqrt(x)sqrt(12/x)-sqrt(12))

    0=-2(2sqrt(3) sqrt(1/x) sqrt(x)-2sqrt(3))

    0=-2*2sqrt(3)( sqrt(1/x) sqrt(x)-1)

    0=-4sqrt(3)( sqrt(1/x) sqrt(x)-1)..........will be equal to zero only if

    sqrt(1/x) sqrt(x)-1=0

    sqrt(1/x) sqrt(x)=1 ........square both sides

    (1/x) x=1

    x/x=1.........will be true only if =>x=1
     
    MathLover1, Feb 6, 2022
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    nycmathguy likes this.
  3. nycmathguy

    nycmathguy

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    Thank you. I know you like the David Cohen book, right? Great math work here.
     
    nycmathguy, Feb 6, 2022
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    MathLover1 likes this.
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