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teller

  • one year ago

Someone check to see if I'm right?

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  1. teller
    • one year ago
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    It would be going up by 4

  2. teller
    • one year ago
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    @jim_thompson5910 mind helping me once again ?I know it's going up by 4 so would it be -n-4?

  3. jim_thompson5910
    • one year ago
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    going up by 4? how did you get that?

  4. teller
    • one year ago
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    -8 to -11 is going up by four and then from -11 to -14 it's going up by four and then from -14 to -17 it's going up by four.

  5. jim_thompson5910
    • one year ago
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    actually the change from 8 to 11 is +3 but we're going from a small negative (-8) to a larger negative (-11) so when we do this, we subtract 3 each time

  6. jim_thompson5910
    • one year ago
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    draw out a number line to check plot -8 and move 3 units to the left to get to -11 moving 3 units to the left means "subtract 3"

  7. teller
    • one year ago
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    so it would be a negative 3 ? so -n-3? or no |dw:1441678898311:dw|

  8. jim_thompson5910
    • one year ago
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    let's check that

  9. jim_thompson5910
    • one year ago
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    if `-n-3` was the function rule, then it should take n = 1 and it should produce -8 as the output but if n = 1, then -n-3 = -1-3 = -4 which is NOT equal to -8 like we want

  10. teller
    • one year ago
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    So what do we do?

  11. jim_thompson5910
    • one year ago
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    let's first find the slope

  12. jim_thompson5910
    • one year ago
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    what's the change in x? the change in y?

  13. teller
    • one year ago
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    3?

  14. teller
    • one year ago
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    well for the input 1 and for the output 3

  15. jim_thompson5910
    • one year ago
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    as x increases by 1, y decreases by 3 change in x = 1 change in y = -3 agreed?

  16. teller
    • one year ago
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    Yes

  17. jim_thompson5910
    • one year ago
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    what would be the slope?

  18. teller
    • one year ago
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    um I don't know not good with slopes.. would it be n+1=-3?

  19. jim_thompson5910
    • one year ago
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    hopefully you wrote down the slope formula I posted on your last question

  20. jim_thompson5910
    • one year ago
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    I would write that in your notes

  21. teller
    • one year ago
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    I don't have it on me mind rewriting it?

  22. jim_thompson5910
    • one year ago
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    ok write it down in your notes or somewhere where you can remember \[\Large \text{Slope} = \frac{\text{Change in y}}{\text{Change in x}}\]

  23. teller
    • one year ago
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    so slope= 1 over -3?

  24. jim_thompson5910
    • one year ago
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    you'll also see this slope formula as well (write this in your notes too) \[\Large \text{Slope} = m = \frac{y_2-y_1}{x_2-x_1}\] m is often used as the slope

  25. jim_thompson5910
    • one year ago
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    you have it backwards it should be -3 over 1

  26. teller
    • one year ago
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    but i thought 1 was y?

  27. jim_thompson5910
    • one year ago
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    |dw:1441679829877:dw|

  28. jim_thompson5910
    • one year ago
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    |dw:1441679911895:dw|

  29. teller
    • one year ago
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    Okay so slope = -3 over 1

  30. jim_thompson5910
    • one year ago
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    |dw:1441679926075:dw|

  31. jim_thompson5910
    • one year ago
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    so that's why change in x = 1 change in y = -3

  32. teller
    • one year ago
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    so would it be n+1-3?

  33. jim_thompson5910
    • one year ago
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    so you see why the slope is -3?

  34. teller
    • one year ago
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    Yea I guess but is my answer correct or no?

  35. jim_thompson5910
    • one year ago
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    no it's not correct

  36. jim_thompson5910
    • one year ago
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    let's say hypothetically that x increased by 2 (instead of 1). The change in y stays the same. What would be the slope this time?

  37. teller
    • one year ago
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    Um slope=-3 over 2..

  38. jim_thompson5910
    • one year ago
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    yes, -3/2 which is equivalent to -1.5

  39. jim_thompson5910
    • one year ago
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    anyways, back to this problem the slope is m = -3

  40. jim_thompson5910
    • one year ago
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    pick any input,output pair you want. Which do you choose?

  41. teller
    • one year ago
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    idk um the original I guess 1 -8

  42. jim_thompson5910
    • one year ago
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    sure let's go with that

  43. jim_thompson5910
    • one year ago
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    m = -3 is the slope x = 1 and y = -8 is the input/output pair

  44. jim_thompson5910
    • one year ago
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    plug those three values into y = mx+b and solve for b

  45. teller
    • one year ago
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    Just to be clear it would be written like this right ? -8=m1+b or no?

  46. jim_thompson5910
    • one year ago
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    replace m with -3

  47. teller
    • one year ago
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    oh okay

  48. teller
    • one year ago
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    so how do I write the one it will just look like -31..

  49. jim_thompson5910
    • one year ago
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    mx is the same as m*x so m*x = -3*1 = -3

  50. teller
    • one year ago
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    oh okay

  51. teller
    • one year ago
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    -5?

  52. jim_thompson5910
    • one year ago
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    yes if you solve -8=-3+b for b, you get b = -5

  53. jim_thompson5910
    • one year ago
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    summary: m = -3 is the slope b = -5 is the y intercept

  54. jim_thompson5910
    • one year ago
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    y = mx+b turns into y = -3x-5

  55. teller
    • one year ago
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    so n x-3-5? is the final answer or no n=-3x-5?

  56. jim_thompson5910
    • one year ago
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    recall from last time, we can replace x with n

  57. jim_thompson5910
    • one year ago
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    so the rule -3x-5 is the same as -3n-5

  58. teller
    • one year ago
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    so -3n-5 is the final answer ?

  59. jim_thompson5910
    • one year ago
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    yeah, plug in n = 1 and you should get -8 plug in n = 2 and you should get -11 etc etc I recommend you actually plug in all of the n values from n = 1 to n = 4 to check them all

  60. teller
    • one year ago
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    Okay can you help me on another one once I try it out?

  61. jim_thompson5910
    • one year ago
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    alright

  62. teller
    • one year ago
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    So input goes up 1 and output goes up 2 so slope = 2/1 so if i take the first combinations 1 and 10 it would be 10=2*1+b which gives me b=8 so would it be 2n+8?

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  63. teller
    • one year ago
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    @jim_thompson5910

  64. jim_thompson5910
    • one year ago
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    very good, you nailed it

  65. jim_thompson5910
    • one year ago
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    to check your answer, you can plug in values of n if n = 1 2n+8 = 2*1 + 8 = 2+8 = 10 so that checks out if n = 2 2*n+8 = 2*2+8 = 12 that checks out as well etc etc

  66. teller
    • one year ago
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    Thank you!You've help me a lot more than what that video will ever do.

  67. jim_thompson5910
    • one year ago
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    I'm glad I could be of help. I'm not sure why the teacher had you watch it when she uses an odd method to find the function rule. If anything, she doesn't mention how to find the generalized rule in terms of n (just how to extend out the table and find outputs for specific inputs).

  68. teller
    • one year ago
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    Yea same I did have a question is the out put goes from a negative to a positive what happens? for example -3 ,-1,1,3 ?

  69. jim_thompson5910
    • one year ago
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    -3 ,-1,1,3 is your list of outputs?

  70. teller
    • one year ago
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    yes

  71. teller
    • one year ago
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    the list of inputs are 1 2 3 4 n

  72. teller
    • one year ago
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    I would say the output is 2 right?

  73. teller
    • one year ago
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    or -2

  74. jim_thompson5910
    • one year ago
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    I think you mean +2 basically you increase the outputs by 2 each time the inputs increase by 1

  75. jim_thompson5910
    • one year ago
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    change in y = +2 change in x = +1 slope = ???

  76. teller
    • one year ago
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    slope = 1 over 2?

  77. jim_thompson5910
    • one year ago
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    you have it flipped again

  78. teller
    • one year ago
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    opps slope =2 over 1

  79. jim_thompson5910
    • one year ago
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    yeah 2/1 = 2

  80. teller
    • one year ago
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    so -3=2*1+b?

  81. teller
    • one year ago
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    which would give me -5

  82. jim_thompson5910
    • one year ago
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    yep

  83. teller
    • one year ago
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    so-5n+2

  84. jim_thompson5910
    • one year ago
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    you mixed up m and b

  85. jim_thompson5910
    • one year ago
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    y = mx+b

  86. teller
    • one year ago
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    What you mean?

  87. teller
    • one year ago
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    -5=2*1+b right?

  88. jim_thompson5910
    • one year ago
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    you found m = 2 and b = -5 so y = mx+b turns into y = 2x-5

  89. teller
    • one year ago
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    oh wait no it's -3 not -5 ,-5 is the answer.

  90. teller
    • one year ago
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    -3=2*1+b

  91. teller
    • one year ago
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    which gave me -5

  92. jim_thompson5910
    • one year ago
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    do you see how I got y = 2x-5 ?

  93. teller
    • one year ago
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    oh wait so it would be 2n-5

  94. jim_thompson5910
    • one year ago
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    yeah you drop the y= part then change x to n

  95. jim_thompson5910
    • one year ago
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    if the input is n, then the output is 2n-5

  96. teller
    • one year ago
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    Yea I was getting confused

  97. jim_thompson5910
    • one year ago
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    but it's all making sense now? or no?

  98. teller
    • one year ago
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    Input 1 output -2 ? slope = -2 over 1 -10=-2*1+b = -12 -2n-12?

  99. jim_thompson5910
    • one year ago
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    going from -10 to -13 is a change of -3

  100. jim_thompson5910
    • one year ago
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    -13 ---> -16 change of -3

  101. jim_thompson5910
    • one year ago
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    and so on

  102. teller
    • one year ago
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    oh okay so -3n-7

  103. jim_thompson5910
    • one year ago
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    correct

  104. teller
    • one year ago
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    Alright thank you so much.That's all I have right now.

  105. jim_thompson5910
    • one year ago
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    glad that it's making sense

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