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Math Help - check my work w/ this word problem

  1. #1
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    check my work w/ this word problem

    ok so i'm not sure if my answers are right

    An open box is to be formed by cutting four identical squares from the coners of a sheet of metal 20cm by 20cm, and folding up the metal to form sides. the capasity of the box must be 588cm^3. what is the side length of the squares?

    this is what i got

    let x be the length of the missing sides

    x(20-2x)(20-2x)=588
    4x^3-80x^2+400x-588=0
    4(x^3-20x^2+100x-147)=0

    where is got a factor of (x-3)

    and was left with x^2-17x+49

    wich gave me x=15.44 or x=1.55

    so the length can be 3cm, 15.44cm, or 1.55cm?
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  2. #2
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    Quote Originally Posted by extraordinarymachine View Post
    ok so i'm not sure if my answers are right

    An open box is to be formed by cutting four identical squares from the coners of a sheet of metal 20cm by 20cm, and folding up the metal to form sides. the capasity of the box must be 588cm^3. what is the side length of the squares?

    this is what i got

    let x be the length of the missing sides

    x(20-2x)(20-2x)=588
    4x^3-80x^2+400x-588=0
    4(x^3-20x^2+100x-147)=0

    where is got a factor of (x-3)

    and was left with x^2-17x+49

    wich gave me x=15.44 or x=1.55

    so the length can be 3cm, 15.44cm, or 1.55cm?
    x = 3

    x^2-17x+49 = 0

    x = \frac{17 \pm \sqrt{93}}{2}

    x= 13.322

    x = 3.678

    is it physically possible for x = 13.322 ???
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