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kandsbbf Group Title

You live near a bridge that goes over a river. The underside of the bridge is an arch that can be modeled with the function y = –0.000471x² + .837x where x and y are measured in feet. How high above the river is the bridge (the top of the arch)? How long is the section of bridge above the arch? The bridge is about 1,777.07 ft. above the river, and the length of the bridge above the arch is about 888.54 ft. The bridge is about 371.85 ft. above the river, and the length of the bridge above the arch is about 1,777.07 ft. The bridge is about 371.85 ft. above the river, and the length of the bri

  • one year ago
  • one year ago

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  1. kandsbbf Group Title
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    The bridge is about 1,777.07 ft. above the river, and the length of the bridge above the arch is about 888.54 ft. The bridge is about 371.85 ft. above the river, and the length of the bridge above the arch is about 1,777.07 ft. The bridge is about 371.85 ft. above the river, and the length of the bridge above the arch is about 888.54 ft. The bridge is about 1,777.07 ft. above the river, and the length of the bridge above the arch is about 371.85 ft.

    • one year ago
  2. kandsbbf Group Title
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    plss help???

    • one year ago
  3. campbell_st Group Title
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    ok... to find the distance spanned by the arch you need to solve it so \[-0.00047x^2 + 0.837x = 0... or... -x(0.00047x - 0.837)\] so x = 0 or 0.837/0.00047 the distance between the points will be the distance spanned. |dw:1358113884987:dw|

    • one year ago
  4. campbell_st Group Title
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    ok... do you know to differentiate..?

    • one year ago
  5. kandsbbf Group Title
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    no lol what is that?

    • one year ago
  6. campbell_st Group Title
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    ok... do you know how to find the line of symmetry of the curve...?

    • one year ago
  7. kandsbbf Group Title
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    no

    • one year ago
  8. campbell_st Group Title
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    what answer did you get got the distance spanned by the bridge..?

    • one year ago
  9. kandsbbf Group Title
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    1,780.851

    • one year ago
  10. kandsbbf Group Title
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    @campbell_st

    • one year ago
  11. campbell_st Group Title
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    oops missed a digit it should be 0.837/0.000471 and you should get 1777.07

    • one year ago
  12. campbell_st Group Title
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    ok so the parabola is symmetric and the highest point of the arch is on the line of symmetry... do you know how to find the line of symmetry..?

    • one year ago
  13. kandsbbf Group Title
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    is it the line that goes down the middle?

    • one year ago
  14. campbell_st Group Title
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    thats it...

    • one year ago
  15. kandsbbf Group Title
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    so how do i figure it out?

    • one year ago
  16. campbell_st Group Title
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    ok... so find half the distance spanned by the arch... then substitute that value into the equation for the bridge... that will give the height does that make sense..

    • one year ago
  17. kandsbbf Group Title
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    soooo divide 1777.07 by 2?

    • one year ago
  18. campbell_st Group Title
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    yep... then substitute it... the highest point is at the centre of the acrch

    • one year ago
  19. kandsbbf Group Title
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    which equation?

    • one year ago
  20. campbell_st Group Title
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    the original equation 0.000471x^2 + 0.837x

    • one year ago
  21. kandsbbf Group Title
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    okay so when i divided it by 2 i got 888.535..... which number do i sub that for in the equation?

    • one year ago
  22. campbell_st Group Title
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    thats correct...

    • one year ago
  23. kandsbbf Group Title
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    so do i sub that in for x?

    • one year ago
  24. campbell_st Group Title
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    yes so its \[-0.000471\times(888.535)^2 + 0.837\times888.535\]

    • one year ago
  25. kandsbbf Group Title
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    so it's D

    • one year ago
  26. campbell_st Group Title
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    what did you get for the height..? the length is 1777.07

    • one year ago
  27. kandsbbf Group Title
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    371.85

    • one year ago
  28. campbell_st Group Title
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    ok... which answer has height 371.85 and length 1777.07

    • one year ago
  29. kandsbbf Group Title
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    B

    • one year ago
  30. campbell_st Group Title
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    thats it.. well done

    • one year ago
  31. kandsbbf Group Title
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    did we answer the last part of the question? How high above the river is the bridge (the top of the arch)? How long is the section of bridge above the arch?

    • one year ago
  32. campbell_st Group Title
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    yes... you have all the answers you need height = 371.85 and length 1777.07

    • one year ago
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