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Math Help - solve quadratic

  1. #1
    Junior Member
    Joined
    Oct 2005
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    29

    baby brain can't cut the mustard

    solve the following quadratic:

    4x^2+17x=6x-2x^2

    looks easy enough, but apparently there's a square root in the answer, which scares my baby brain.
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  2. #2
    Junior Member
    Joined
    Aug 2005
    Posts
    53
    Hi,

    4x^2+17x=6x-2x^2.

    When you have x^2 and x in the same equality put always everything =0.

    Why not isolate x from the beggining, well because we have different powers of x and which one do we isolate... Beep! can't do.

    So, we use the trick putting everything=0. So we transfer the 6x (which is positive it gets negative on the other side and the opposite goes with the -2x^2). We get : 4x^2+17x-6x+2x^2=0 (nothing left on the right).
    We add the x^2 together and the x together and get 6x^2+11x=0 so we take out an x and get x(6x+11)=0 so to get 0 we must have either x=0 or (6x+11)=0. So if x=0 well, x=0. And if 6x+11=0 so x=-11/6. So two possible answer: 0 or -11/6. No square roots needed.
    Try them in 4x^2+17x=6x-2x^2 and you'll get an equality (either all x=0 or all x = -11/6 not at the same time) !!!
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  3. #3
    Junior Member
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    Oct 2005
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    Thank you! I owe you one
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