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anonymous

  • 4 years ago

Help I am trying to study for a test.... given the following function f(x)=2x^2-4x-5\ 1) determine the vertex 2) list the axis of symmetry 3) calculate the y-intercept 4) use the axis of symmetry and the y-intercept to find an additional point on the graph

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  1. Mertsj
    • 4 years ago
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    Do you know that it's a parabola?

  2. anonymous
    • 4 years ago
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    No that is all the study paper give us was this ? exactly like it is

  3. Mertsj
    • 4 years ago
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    What have you been studying in your class?

  4. anonymous
    • 4 years ago
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    This is the start of the class and we are having to take a pretest

  5. anonymous
    • 4 years ago
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    it is college algebra or precalculus

  6. Mertsj
    • 4 years ago
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    well then your teacher is trying to find out what you know so just do the best you can.

  7. anonymous
    • 4 years ago
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    well out textbook does not really give a good explanation of anything

  8. Mertsj
    • 4 years ago
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    So do you want to work through this problem?

  9. anonymous
    • 4 years ago
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    i would appreciate any help i can get

  10. Mertsj
    • 4 years ago
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    This is the equation of a parabola. The x coordinate of the vertex can be found using the formula x = -b/2a

  11. Mertsj
    • 4 years ago
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    which in this case is 4/4 or 1

  12. Mertsj
    • 4 years ago
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    Now you can find the y coordinate of the vertex by replacing x with 1 and finding f(x)

  13. Mertsj
    • 4 years ago
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    f(1)=-7 So the vertex is (1,-7)

  14. anonymous
    • 4 years ago
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    so how do u come up with the 7

  15. Mertsj
    • 4 years ago
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    The axis of symmetry is the vertical line through the vertex so it is x = 1

  16. Mertsj
    • 4 years ago
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    Did you replace x with 1 in your equation?

  17. anonymous
    • 4 years ago
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    o no

  18. Mertsj
    • 4 years ago
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    \[f(x)=2(1)^2-4(1)-5=2-4-5=2-9=-7\]

  19. Mertsj
    • 4 years ago
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    Are you reading what I write?

  20. Mertsj
    • 4 years ago
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    Now you can find the y coordinate of the vertex by replacing x with 1 and finding f(x)

  21. anonymous
    • 4 years ago
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    yes I am

  22. Mertsj
    • 4 years ago
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    So now we are ready for 3 which is calculate the y intercept. We can find the y intercept by letting x = 0. So replace x with 0

  23. Mertsj
    • 4 years ago
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    Did you get -5? So the y intercept is (0,-5)

  24. anonymous
    • 4 years ago
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    just a sec

  25. Mertsj
    • 4 years ago
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    one second granted

  26. anonymous
    • 4 years ago
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    ok 0 cancels so i end up with -5

  27. Mertsj
    • 4 years ago
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    Yep

  28. Mertsj
    • 4 years ago
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    Now we're ready for the last part. And for that we need to put the info we have on a graph.

  29. Mertsj
    • 4 years ago
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    |dw:1328758359627:dw|

  30. Mertsj
    • 4 years ago
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    The axis of symmetry helps us find another point because for every point to the left of the axis, there is a corresponding point to the right.

  31. Mertsj
    • 4 years ago
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    So if we start at the y intercept and go 1 unit to the right, we come to the aos. If we go one more unit to the right, there will be another point.

  32. Mertsj
    • 4 years ago
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    |dw:1328758665785:dw|

  33. Mertsj
    • 4 years ago
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    So another point on the graph is (2,-5)

  34. anonymous
    • 4 years ago
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    so unless it is stated you either move to the left or right 1 point

  35. Mertsj
    • 4 years ago
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    You move however many units it takes to get to the axis of symmetry.

  36. anonymous
    • 4 years ago
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    o ok...thank u for ur help

  37. Mertsj
    • 4 years ago
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    yw

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