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kandsbbf

  • one year ago

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

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  1. kandsbbf
    • one year ago
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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.

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

  3. campbell_st
    • one year ago
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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|

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

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

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

  7. kandsbbf
    • one year ago
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    no

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

  9. kandsbbf
    • one year ago
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    1,780.851

  10. kandsbbf
    • one year ago
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    @campbell_st

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

  12. campbell_st
    • one year ago
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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..?

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

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

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

  16. campbell_st
    • one year ago
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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..

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

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

  19. kandsbbf
    • one year ago
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    which equation?

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

  21. kandsbbf
    • one year ago
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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?

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

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

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

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

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

  27. kandsbbf
    • one year ago
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    371.85

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

  29. kandsbbf
    • one year ago
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    B

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

  31. kandsbbf
    • one year ago
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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?

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

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