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Shido88

  • 3 years ago

Find the Vertex: f(x)= -3x^2-7x+6

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  1. Shido88
    • 3 years ago
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    @saifoo.khan helpppp lol

  2. saifoo.khan
    • 3 years ago
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    Hey. To find vertex there's a shortcut.

  3. Shido88
    • 3 years ago
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    uh huh

  4. saifoo.khan
    • 3 years ago
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    to find the x-cordinate, use this formula: -b/2a

  5. saifoo.khan
    • 3 years ago
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    -(-7)/2(-3)

  6. Shido88
    • 3 years ago
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    that will give me the vertex ?

  7. saifoo.khan
    • 3 years ago
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    Yes. "x-cordinate" of vertex.

  8. saifoo.khan
    • 3 years ago
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    Solve it first..

  9. Shido88
    • 3 years ago
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    kk hold on :)

  10. saifoo.khan
    • 3 years ago
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    Holding.. :)

  11. Shido88
    • 3 years ago
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    got 7/6

  12. Shido88
    • 3 years ago
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    vertex is (h,k) right? so i believe that is the "h" ?

  13. saifoo.khan
    • 3 years ago
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    Perfect. ^

  14. saifoo.khan
    • 3 years ago
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    Find k now.

  15. Shido88
    • 3 years ago
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    how to find k lol ?

  16. saifoo.khan
    • 3 years ago
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    Lol. Use GOogle. Jk.

  17. Shido88
    • 3 years ago
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    i got it lmao :))

  18. Shido88
    • 3 years ago
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    hold on

  19. saifoo.khan
    • 3 years ago
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    Okay. so now use 7/6 to find it. y = -3x^2-7x+6 y = -3(7/6)^2 -7(7/6) + 6 solve.

  20. Shido88
    • 3 years ago
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    got decimal :( hate decimal

  21. Shido88
    • 3 years ago
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    so the vertex would be : (7/6, -6.24) ?

  22. saifoo.khan
    • 3 years ago
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    Should be 121/12

  23. Shido88
    • 3 years ago
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    wtf ?

  24. Shido88
    • 3 years ago
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    how? :O

  25. Shido88
    • 3 years ago
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    -156/25

  26. Shido88
    • 3 years ago
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    hey come back here >:o

  27. saifoo.khan
    • 3 years ago
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    VERTEX SHOULD BE -7/6. -_-

  28. saifoo.khan
    • 3 years ago
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    THE X-CORDINATE.

  29. Shido88
    • 3 years ago
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    CALM DOWN !! CAPS WAR XD

  30. saifoo.khan
    • 3 years ago
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    ONE NEGATIVE SIGN RUINS EVERYTHING. >_<

  31. Shido88
    • 3 years ago
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    so -7/6 because its opposite of 7/6 ?

  32. Shido88
    • 3 years ago
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    you suppose to change it everytime ?

  33. Shido88
    • 3 years ago
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    how come my teacher didn't change it -_____-

  34. saifoo.khan
    • 3 years ago
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    No. we calculated the x-cordinate wrong in the first place.

  35. Shido88
    • 3 years ago
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    oh....XD

  36. saifoo.khan
    • 3 years ago
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    \[-\frac{b}{2a} \to -\frac{(-7)}{2(-3)}\to \frac{7}{-6} \to -\frac 76\]

  37. Shido88
    • 3 years ago
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    ohhhhhhhhh i see now lmao hhahaha :D

  38. Shido88
    • 3 years ago
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    omfg...my whole problem is wrong, thanks saif ! lol : XD

  39. Shido88
    • 3 years ago
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    +99 medals

  40. saifoo.khan
    • 3 years ago
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    ;D Thanks.

  41. Shido88
    • 3 years ago
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    hmm instead of 121/10 should i just leave it as 10.08 cuz i have to graph this afterward ?

  42. Shido88
    • 3 years ago
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    great now i gotta calculate x-int and y-int :| let see......

  43. saifoo.khan
    • 3 years ago
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    Sure. Same thing. Depends on in what format your teacher wants

  44. Shido88
    • 3 years ago
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    stay there.. lol

  45. saifoo.khan
    • 3 years ago
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    Lol. okays.

  46. Shido88
    • 3 years ago
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    stuck lol....find x-intercept?

  47. Shido88
    • 3 years ago
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    i know let y=0

  48. Shido88
    • 3 years ago
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    0=-3x^2-7x+6

  49. Shido88
    • 3 years ago
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    -6=-3x^2-7x <-----stuck here..

  50. saifoo.khan
    • 3 years ago
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    Use quadratic formula

  51. Shido88
    • 3 years ago
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    oh yee

  52. saifoo.khan
    • 3 years ago
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    https://www.khanacademy.org/math/algebra/quadratics/quadratic_formula/v/quadratic-formula-1

  53. Shido88
    • 3 years ago
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    but the way my teacher did it was to set y=0 and just add and divide stuff on left and right side...which is confusing but i suppose we can use quadratic aswell :)

  54. saifoo.khan
    • 3 years ago
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    Your teacher must have used the "completing the square" method. It's hella confusing. It confuses me too. :/

  55. Shido88
    • 3 years ago
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    yeah thats what that was, completing the square lol.... ok i got y= 7+- sqrt(-23)/-6 and what's next ?

  56. Shido88
    • 3 years ago
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    i dont think u can reduce it down or anything right? and u can't even square root a negative

  57. saifoo.khan
    • 3 years ago
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    https://www.khanacademy.org/math/algebra/quadratics/quadratic_formula/v/quadratic-formula-1

  58. saifoo.khan
    • 3 years ago
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    No. We can't reduce.

  59. saifoo.khan
    • 3 years ago
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    u can't even square root a negative Yes you're very right.

  60. Shido88
    • 3 years ago
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    ohh i get it, it's 7+- 23i/-6

  61. saifoo.khan
    • 3 years ago
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    Roots are: -14 and 0.

  62. saifoo.khan
    • 3 years ago
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    Roots are: -3 and 2/3

  63. Shido88
    • 3 years ago
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    what? @_@

  64. Shido88
    • 3 years ago
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    was that you on the video? https://www.khanacademy.org/math/algebra/quadratics/quadratic_formula/v/quadratic-formula-1

  65. saifoo.khan
    • 3 years ago
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    Haha. Ofcourse not.

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