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Right triangle

  1. Mar 18, 2009 #1
    A large right triangle has a hypotonuse of 2000x+1125. The other sides are 2000x-1125 and x. solve for x. I have tried this with pythagoreon theorem and solving a quadratic and what not but cant get it to work out. maybe i am just making a simple mistake but i cant get it to work out.
     
  2. jcsd
  3. Mar 18, 2009 #2
    Well you should get (2000x-1125)2+x2 = (2000x+1125)2 from the pythagoreon. Then expand. What did you get from your expansion?
     
  4. Mar 18, 2009 #3
    i get simply x^2-9000000x=0. im thinking this is wrong though because to use the quadratic formula would give you 9000000-9000000, which equals 0/2, or 0.
     
  5. Mar 18, 2009 #4
    Well you have (2000x-1125)2+x2 = (2000x+1125)2

    and (2000x-1125)2 = 4000000x2-2250000x+1265625 and (2000x+1125)2 = 4000000x2+2250000x+1265625.

    How does this fall out?

    Your equation above is incorrect. Further, you don't really need the quadratic equation. Anything of the form ax2 - bx = 0 = x(ax - b) so x = 0 or b/a. Also I don't think you're doing the quadratic formula correctly, you shouldn't have gotten 9000000-9000000. However 0 is a possible value for x.

    Does that help?
     
  6. Mar 18, 2009 #5
    wha happens to me was when i worked out the other side stuff got cancelled. ill have a go at it, take wha you said and let you know how it goes.
     
  7. Mar 18, 2009 #6
    Well most of it should cancel out and you should get x2 - 4500000x = 0.

    Is that what you got? If so what is the answer?
     
  8. Mar 19, 2009 #7
    this has me very confused, even though it seems like it should be easy. when i expand from the pythagorean theorem i get x^2-9000000x=0, put that in quadratic formula and i get either 9000000 or 0. which doesnt seem right and doesnt work when i apply it to the triangle. what am i doing wrong? Can someone post up an answer just so i can tr to work through it and see where i went wrong because this is driving me nuts.
     
  9. Mar 19, 2009 #8
    You're right; I did math poorly (sorry!) and forgot to double the middle term.

    You have (2000x-1125)2 = 4000000x2-4500000x+1265625 and (2000x+1125)2 = 4000000x2+4500000x+1265625.

    So (2000x+1125)2 = (2000x-1125)2 + x2 gives us 4000000x2+4500000x+1265625 = 4000000x2-4500000x+1265625 + x2

    Like terms cancel so we get 4500000x = -4500000x + x2 or x2 - 9000000x = 0 or x(x-9000000) = 0 or x = 0, 9000000.

    Make sense?
     
  10. Mar 19, 2009 #9
    es that makes sense, that is what i got. i must have done some bad math too, because i didn't think 9000000 would work when applied to the triangle,b ut i now see it does. thanks for the help.
     
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