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Math Help - Solving the Diagnol of a Rectangle

  1. #1
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    Solving the Diagnol of a Rectangle

    The width of a rectangle is 1 less than twice its length. If the area of the rectangle is 40 cm, what is the length of the diagonal?

    Note: Your answer must be a number. It may not contain any arithmetic operations.

    The length of the diagonal is....

    I need help with this problem :/

    the width is = 2L - 1
    length is L

    so.... (2L-1)(L) = 40

    2L^2 - 1L = 40

    2L^2 - 1L - 40 = 0
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  2. #2
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    Re: Solving the Diagnol of a Rectangle

    Just solve for L. How would you find L?

    Once you've found L, find 2L - 1, then find the diagonal via Pythagorean theorem.
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  3. #3
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    Re: Solving the Diagnol of a Rectangle

    i cant factor it. therefor should i use the quadratic formula to solve for L
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  4. #4
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    Re: Solving the Diagnol of a Rectangle

    Sure.
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