A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • one year ago

okay help with this problem and then one more and I wont need anymore help tonight. (2-3i(3-i)-(4-i)(4+i)

  • This Question is Open
  1. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[(2-3i)(3-i)-(4-i)(4+i)\]

  2. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    (2-3i)(3-i)-(4-i)(4+i)

  3. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    theres supposed to be one more parenthases after 3i

  4. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    am i foiling this or is that not the right way to go about this problem?

  5. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    you can FOIL or use the table like last time. Which option works best for you?

  6. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    foil the table is a little confusing.

  7. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok what do you get when you FOIL (2-3i)(3-i)

  8. bradely
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    (2 -3i)(3-i)-(4-i)(4+i) (2)(3-i)-(3i)(3-i)-(4^2-i^2) Multiply find the value Note i^2 = -1 Source: mathskey.com

  9. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    3-11i

  10. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    correct

  11. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    how about `(4-i)(4+i)` ?

  12. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    that is 15

  13. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    brb

  14. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    not 15, but you are close

  15. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    try again

  16. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    okay

  17. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    where did i go wrong with my problem i will show you my work.

  18. bradely
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    (4-i)(4+i) (a-b)(a+b) =a^2-b^2 4^2 -i^2 16-(-1)=17

  19. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    could the answer be 187i+51?

  20. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1441072256502:dw|

  21. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i^2 is -1 so \(\Large 16-\color{red}{i^2}\) turns into \(\Large 16-\color{red}{(-1)}\)

  22. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    im not sure @sayomi

  23. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Do you see what I mean @huntergirl1 ?

  24. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes now i do @jim_thompson5910

  25. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok great, so 16-(-1) = 16+1 = 17 --------------------- \[\large \color{red}{(2-3i)(3-i)}-\color{blue}{(4-i)(4+i)} =\color{red}{3-11i}-\color{blue}{17} = -14-11i\]

  26. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    @sayomi you were correct and yes @jim_thompson5910 i do understand

  27. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I'm glad it's making sense

  28. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so the ending result is 51-187i

  29. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    okay do you wnt me to start a new window for the next problem? or to place it here?

  30. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    how are you getting `51-187i` ?

  31. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I wrote the answer above

  32. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    bc you put 17 back into the problem

  33. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    are you saying that they wanted you to multiply `(2-3i)(3-i)` and `(4-i)(4+i)` ??

  34. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    actually i put those answers both into the website they were both incorrect

  35. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    hwy was the answer supposed to be -14-11i?

  36. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    why

  37. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    because the 3 and -17 combine to -14

  38. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    (3-11i) - (17) = 3-11i - 17 = (3-17) + (-11i) = -14 - 11i

  39. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    oh okay.

  40. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    will you be on to check a few more problems before I submit them?

  41. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    sure

  42. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    thank you!!!!!!!!!!!!

  43. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    no problem

  44. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    okay i have one to check its similar to the last problem

  45. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1441074082197:dw|

  46. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    what did i do wrong?

  47. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    you didn't foil correctly

  48. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    okay i guess the sqrt part mixed me up

  49. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i also tried the box method too

  50. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1441074547608:dw|

  51. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    what we do is make a 2x2 box 2 rows and 2 columns the terms of each factor will go along the outside like this |dw:1441074595637:dw|

  52. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    agreed so far?

  53. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    okay thats how i started it on my paper too

  54. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok go ahead and fill it out

  55. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1441074610390:dw|

  56. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    -4 times \(\large -i\sqrt{2}\) should be \(\large +4i\sqrt{2}\) the two negatives cancel |dw:1441074917203:dw|

  57. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    right?

  58. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    same with the -i and -i being multiplied in the lower right box |dw:1441074956036:dw|

  59. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so instead of a negative is a possitive

  60. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so after filling the boxes and simplifying the expressions in each box, we end up with |dw:1441075014939:dw| since \[\Large i^2*\sqrt{4} = -1*2 = -2\]

  61. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    okay

  62. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so is the answer 18 instead?

  63. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    no :( dang it please help me i have until 11:50 to submit these

  64. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    now add up the terms inside the boxes \[\Large 16 + 4i\sqrt{2} + 4i\sqrt{2}+(-2) = 14+8i\sqrt{2}\]

  65. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1441075415932:dw|

  66. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    okay that makes since

  67. jim_thompson5910
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1441075435745:dw|