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Math Help - Word problem - quadratics

  1. #1
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    Word problem - quadratics

    The hypotenuse of a right angle triangle is 15 cm. the sum of the legs of the triangle is 21 cm. Find the legs of the triangle.

    How do I solve this?

    ps I have to solve this using the quadratic formula
    Last edited by dancingqueen9; July 13th 2008 at 05:52 PM.
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  2. #2
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    I would figure that by scaling, you can make  \frac{15}{3}=5 making the hypotenuse 5, then knowing this, and the 3-4-5 rule, you could make the legs, 3 and 4 respectively, then to convert back to the parameters of the problem, you'd multiply back by 3, giving you 3*3 = 9 and  4*3 = 12 which if added, 9+12 = 21 give you the 21 cm stated in the problem.
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  3. #3
    MHF Contributor Mathstud28's Avatar
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    Quote Originally Posted by dancingqueen9 View Post
    The hypotenuse of a right angle triangle is 15 cm. the sum of the legs of the triangle is 21 cm. Find the legs of the triangle.

    How do I solve this?
    Let a and b denote the legs of the right triangle, we know that

    a+b=21

    and

    a^2+b^2=225

    Now solve that system of equations

    You should get (its in white so you don't have to see it, if you wish to just highlight below)
    x=9 and y=12 or y=9 and x=12...they are describing the same triangle
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  4. #4
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    Alright, thanx guys!
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