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Thread: Find all ordered triples (x,y,z)

  1. #1

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    Find all ordered triples (x,y,z)

    Find all ordered triples (x,y,z) to:

    x+yz=6
    y+xz=6
    z+xy=6

    Show proof!!
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  2. #2
    transcendental analytic kedaman's Avatar
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    z=6-xy
    x=6-zy
    y+x(6-xy)=6
    y+(6-zy)(6-(6-zy)y)=6
    y+(6-zy)(6-6y-zy^2)=6
    y+36-36y-6zy^2-6zy+6zy^2+z^2y^3=6
    -35y-30-6zy+z^2y^3=0
    z=-6y/2y^3 +- sqrt( (-6y/2y^3)^2 - 35y-30)
    z=-3/y^2 +- sqrt( 9/y^4 - 35y-30)
    z= -3/y^2 + sqrt( 9/y^4 - 35y-30), x=6- 3/y - sqrt( 9/y^2 - 35y^3-30y^2) or
    z= -3/y^2 - sqrt( 9/y^4 - 35y-30), x=6- 3/y + sqrt( 9/y^2 - 35y^3-30y^2)
    for all pairs of X, Y and Z respectively, where the remaining variable is in R.
    { (x,y,z)|y in R, z= -3/y^2 + sqrt( 9/y^4 - 35y-30), x=6- 3/y - sqrt( 9/y^2 - 35y^3-30y^2) or
    z= -3/y^2 - sqrt( 9/y^4 - 35y-30), x=6- 3/y + sqrt( 9/y^2 - 35y^3-30y^2) | (x,y,z) in permuations of(X,Y,Z) }
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