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RealityWillSlapYou

  • 3 years ago

Select the equations that are parallel and perpendicular to y = −3x − 1 and that pass through the point (3, 1). A. parallel: y = −3x + 6 perpendicular: y = (1/3)x + 2(2/3) B. parallel: y = −3x + 10 perpendicular: y = (1/3)x C. parallel: y = -(1/3)x perpendicular: y = −3x D. parallel: y = (1/3)x + 1 perpendicular: y = 3x − 1

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  1. RealityWillSlapYou
    • 3 years ago
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    @SmokeysTheName, Right here!

  2. SmokeysTheName
    • 3 years ago
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    ohhh man, remember i said i couldn't help? but here @phi might be able to

  3. RealityWillSlapYou
    • 3 years ago
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    Oh, oops! Sorry about that.... :)

  4. SmokeysTheName
    • 3 years ago
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    thats fine (:

  5. SmokeysTheName
    • 3 years ago
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    @hero can you help with this?

  6. Hero
    • 3 years ago
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    Pretty easy stuff @SmokeysTheName

  7. SmokeysTheName
    • 3 years ago
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    its been forever since ive done this and i can't remember /: so can you help him?

  8. Hero
    • 3 years ago
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    Hint: m1 x m2 = -1

  9. RealityWillSlapYou
    • 3 years ago
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    Umm.... I not really sure.. :|

  10. Hero
    • 3 years ago
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    m1 = -3 So m2 has to be a number such that when multiplied by m1, their product is -1.

  11. RealityWillSlapYou
    • 3 years ago
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    -1?

  12. RealityWillSlapYou
    • 3 years ago
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    Then 1 x -1 = -1

  13. RealityWillSlapYou
    • 3 years ago
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    Right?

  14. Hero
    • 3 years ago
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    m1 = -3 Multiply -3 by something to get -1

  15. RealityWillSlapYou
    • 3 years ago
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    I have no clue..... :|

  16. SmokeysTheName
    • 3 years ago
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    is that even possible @hero?

  17. Hero
    • 3 years ago
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    -3 x 1/3 = -1

  18. Hero
    • 3 years ago
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    Yes, it is possible.

  19. Hero
    • 3 years ago
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    So that's basically the slope of the second equation.

  20. SmokeysTheName
    • 3 years ago
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    oh yeah xD lol i dont like fractions so i didnt think of it. my bad okay ill stay out of this..

  21. RealityWillSlapYou
    • 3 years ago
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    Oh, why is math so hard for me to understand?!

  22. Hero
    • 3 years ago
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    So now, you have the slope and the point. Use the point slope formula to figure out the value of b.

  23. RealityWillSlapYou
    • 3 years ago
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    Y U NO WORK FOR ME MATH?! (ノಠ益ಠ)ノ

  24. phi
    • 3 years ago
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    sometimes it helps to watch these videos http://www.khanacademy.org/math/trigonometry/graphs/parallel_perpendicular/v/equations-of-parallel-and-perpendicular-lines

  25. SmokeysTheName
    • 3 years ago
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    phi is right, khan acad vids are great to watch

  26. RealityWillSlapYou
    • 3 years ago
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    @phi, in the video he was using two points and my question only has one point so how can I solve it the same way?

  27. phi
    • 3 years ago
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    at the very end he does a problem like yours.

  28. RealityWillSlapYou
    • 3 years ago
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    Oh, my video sever crashed after the second equation.

  29. phi
    • 3 years ago
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    but this video assumes you know about slopes and equations of lines (he has videos on all of that) for you problem, you should know that when you see y = mx +b m is the slope. the number multiplying the x is the slope

  30. RealityWillSlapYou
    • 3 years ago
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    I will start it back up again, but it will take 2 min.

  31. RealityWillSlapYou
    • 3 years ago
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    I tried to solve it (I think I did it wrong) and is it C?

  32. phi
    • 3 years ago
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    for you problem, you should know that when you see y = mx +b m is the slope. the number multiplying the x is the slope so what is the slope of your line y = −3x − 1 ?

  33. RealityWillSlapYou
    • 3 years ago
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    -3?

  34. phi
    • 3 years ago
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    do you see a number in front of the x ?

  35. RealityWillSlapYou
    • 3 years ago
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    So is the answer B?

  36. phi
    • 3 years ago
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    yes, -3 is the slope (that is why people came up with this kind of equation, you can read off the slope easily)

  37. phi
    • 3 years ago
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    from the video, you learned that parallel lines have what kind of slope ?

  38. RealityWillSlapYou
    • 3 years ago
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    The same slope

  39. phi
    • 3 years ago
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    look at your 4 choices. which choices have the correct slope of -3 for the parallel line ?

  40. RealityWillSlapYou
    • 3 years ago
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    Well it's A or B....... I think it's B

  41. phi
    • 3 years ago
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    no need to guess. now for the perpendicular line. Its slope is the negative inverse (or negative reciprocal) that means "flip" the slope and multiply by -1. For example if you had slope =2 \[ \frac{2}{1} ->- \frac{1}{2}\] can you do that for -3 ?

  42. RealityWillSlapYou
    • 3 years ago
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    \[\frac{ 3 }{ 1 }?\]

  43. RealityWillSlapYou
    • 3 years ago
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    Or\[\frac{ 1 }{ 3 }?\]

  44. phi
    • 3 years ago
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    3/1 is 3 start with -3 or -3/1 minus it : - -3/1 is +3/1 now flip it : 1/3 you know you did it right if it is the opposite sign of -3, and it's "upside down"

  45. RealityWillSlapYou
    • 3 years ago
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    Okay

  46. phi
    • 3 years ago
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    the slope of the perpendicular is 1/3 look at choices A or B. can we rule out either choice because it does not have 1/3 for the slope of the perpendicular line ?

  47. RealityWillSlapYou
    • 3 years ago
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    We can rule out A, right?

  48. phi
    • 3 years ago
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    for choice A, what is the number in front of the x for the perpendicular line ?

  49. RealityWillSlapYou
    • 3 years ago
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    -3

  50. phi
    • 3 years ago
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    that is the parallel line

  51. phi
    • 3 years ago
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    A. parallel: y = −3x + 6 perpendicular: y = (1/3)x + 2(2/3)

  52. RealityWillSlapYou
    • 3 years ago
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    So we rule out B?

  53. phi
    • 3 years ago
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    B. parallel: y = −3x + 10 perpendicular: y = (1/3)x what is the slope for the perpendicular line ?

  54. RealityWillSlapYou
    • 3 years ago
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    1/3

  55. phi
    • 3 years ago
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    so both A and B pass. we have to use the last bit of info pass through the point (3, 1) that says that when x=3 y must = 1 test choice B, perpendicular (because it looks the easiest) y = (1/3)x replace x with 3 and do the arithmetic what do you get ?

  56. phi
    • 3 years ago
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    replace x with 3 that means wherever you see an x, put a 3 in its place.

  57. RealityWillSlapYou
    • 3 years ago
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    okay give me a min.

  58. RealityWillSlapYou
    • 3 years ago
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    y = (1/3)3

  59. RealityWillSlapYou
    • 3 years ago
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    ??

  60. phi
    • 3 years ago
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    yes, \[y= \frac{1}{3} \cdot 3 \] you can think of the 3 as 3/1 or \[y= \frac{1}{3} \cdot \frac{3}{1} \] when you multiply fractions, multiply top times top and bottom times bottom you get \[y= \frac{3}{3} \] can you simplify this ?

  61. RealityWillSlapYou
    • 3 years ago
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    y = 1

  62. phi
    • 3 years ago
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    so (3,1) is on this line. this is the choice

  63. phi
    • 3 years ago
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    if we put x=3 in choice A, we will not get y=1 btw, we should check the parallel line can you do that ? parallel: y = −3x + 10 what do you get if you replace x with 3

  64. RealityWillSlapYou
    • 3 years ago
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    -9

  65. phi
    • 3 years ago
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    what about the +10 ?

  66. RealityWillSlapYou
    • 3 years ago
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    1

  67. phi
    • 3 years ago
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    y = −3x + 10 if this does not give you y=1 when x=3 then it is not the line. But it does give y=1 so choice B. Does any of this make sense ?

  68. RealityWillSlapYou
    • 3 years ago
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    Yeah....

  69. RealityWillSlapYou
    • 3 years ago
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    How many more questions can you help me with?

  70. phi
    • 3 years ago
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    how many do you have ?

  71. RealityWillSlapYou
    • 3 years ago
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    Three, but I'm really bad at math.

  72. phi
    • 3 years ago
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    did you post them yet ?

  73. RealityWillSlapYou
    • 3 years ago
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    I posted one of them in algebra

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