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anonymous

  • 5 years ago

3x-7y=21. Need the 3 ordered pairs where #1: x=0, is __ #2: y=0, is __ #3: y=-6, is __.

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  1. anonymous
    • 5 years ago
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    ok, so for the first one, you would plug in 0( which is x) in the equation.: 3(0)-7y=21 0-7y=21 y=21/-7 y=-3, so first ordered pair would be (0, -7) for the second one you would plug in0 for y this time, and in the third one you would plug in -6 for why, and solve for x on that too. then you have your three ordered pairs

  2. anonymous
    • 5 years ago
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    I am still not getting it so need more help

  3. anonymous
    • 5 years ago
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    ok, so lets do the second one

  4. anonymous
    • 5 years ago
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    ok i tried but got lost

  5. anonymous
    • 5 years ago
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    the second one says y= 0 so we are going to plug in 0 for the y, in the function: 3x-7y=21 so when we plug in 0 for y, the function now says: 3x-7(0)=21 next we multiply 0 times 7, so we get: 3x-0=21, which is basically 3x=21 next, we finaly divide 3 on both sides to get x by itself x=21/3 which is x =7

  6. anonymous
    • 5 years ago
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    so now that we know that x=7 , when y=0, the ordered pair is in the form of (x,y) which in this case, it would be (7, 0). that is your second set of points. did you understand this?

  7. anonymous
    • 5 years ago
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    well when i did it it was a little different but it did not look right but had the same answer

  8. anonymous
    • 5 years ago
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    for the last one i started with 3x-7(-6)=21

  9. anonymous
    • 5 years ago
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    then i had 3x-42=21

  10. anonymous
    • 5 years ago
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    ok wait a sec

  11. anonymous
    • 5 years ago
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    whats -7 *-6?

  12. anonymous
    • 5 years ago
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    don't I replace the y with -6?

  13. anonymous
    • 5 years ago
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    yes, but what is -7 times -6. can you hold up for a sec

  14. anonymous
    • 5 years ago
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    sure

  15. anonymous
    • 5 years ago
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    3x-7(-6)=21 is the correct next step, but what do you get when you multiply negative 7 times negative 6?

  16. anonymous
    • 5 years ago
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    you get positive 42

  17. anonymous
    • 5 years ago
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    so you should have 3x-42=21

  18. anonymous
    • 5 years ago
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    no, its going to be 3x+42=21 because we got positive 42, not negative 42

  19. anonymous
    • 5 years ago
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    ok i see

  20. anonymous
    • 5 years ago
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    yes 3x+42=21, what do we do next?

  21. anonymous
    • 5 years ago
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    get x by itself by using 3

  22. anonymous
    • 5 years ago
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    OK WAIT

  23. anonymous
    • 5 years ago
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    we still have that 42 there, and we need to get rid of it, so how do we get rid of that 42: 3x+42=21

  24. anonymous
    • 5 years ago
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    3x +42 -42 = 21 +42 - 42

  25. anonymous
    • 5 years ago
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    there we go! and what do we get?

  26. anonymous
    • 5 years ago
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    3x=21

  27. anonymous
    • 5 years ago
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    wait whats 21-42? -21!

  28. anonymous
    • 5 years ago
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    huh?

  29. anonymous
    • 5 years ago
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    I thought the 42s cancelled each other out

  30. anonymous
    • 5 years ago
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    yes, but its not 3x=21 its 3x=-21

  31. anonymous
    • 5 years ago
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    ok I don't get it

  32. anonymous
    • 5 years ago
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    so this is what you got 3x +42 -42 = 21 +42 - 42

  33. anonymous
    • 5 years ago
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    right

  34. anonymous
    • 5 years ago
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    why did you add 42 both sides? you were only supposed to subtract 42 on both sides. try it again,

  35. anonymous
    • 5 years ago
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    3x +42 -42 = 21- 42 is what you should get

  36. anonymous
    • 5 years ago
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    ok i put an extra one in there

  37. anonymous
    • 5 years ago
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    exactly so figure it from this: 3x +42 -42 = 21- 42

  38. anonymous
    • 5 years ago
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    ok so 3x +42 -42 = 0

  39. anonymous
    • 5 years ago
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    21 -42= -21

  40. anonymous
    • 5 years ago
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    yes so it should be 3x=-21

  41. anonymous
    • 5 years ago
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    so (-21,-6) is the ordered pair

  42. anonymous
    • 5 years ago
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    we stil need to find x! we were left with 3x=-21 ! remember we need to get x by itself!

  43. anonymous
    • 5 years ago
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    ok so we us 3 on both sides

  44. anonymous
    • 5 years ago
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    we divide 3 by both sides

  45. anonymous
    • 5 years ago
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    damn this thing hangs up on me a lot. so we should end up with x = 21

  46. anonymous
    • 5 years ago
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    whats -21/3?

  47. anonymous
    • 5 years ago
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    -7

  48. anonymous
    • 5 years ago
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    so x=-7. gosh, what grade are you in? and math level?

  49. anonymous
    • 5 years ago
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    I just started college last year Oct and I graduated in 1969 and had just basic math. I was able to transfer 52 credits from my military career. So I am about a late sophmore or early junior. math is 092 which is pre algebra

  50. anonymous
    • 5 years ago
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    college 0.0i learned this in 6th and 7th.

  51. anonymous
    • 5 years ago
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    ya I know but I have never had algebra before

  52. anonymous
    • 5 years ago
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    and im in 9th. yaaay! i feel so smart!

  53. anonymous
    • 5 years ago
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    when i was in high school we did not have algebra and geometry. it did not exist

  54. anonymous
    • 5 years ago
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    so when i was in 12th they were just starting it as an elective.

  55. anonymous
    • 5 years ago
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    I guess that is why it is so hard for me.

  56. anonymous
    • 5 years ago
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    whoa! it really does amaze me how far human intelligence has gone. I cant imagine how advanced our human race will be in he next 40 years

  57. anonymous
    • 5 years ago
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    ya i know. i wish there was a way for me to shock the heck out my brain so it would be easier for me to learn

  58. anonymous
    • 5 years ago
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    lol, so do i! agh sooo much work!

  59. anonymous
    • 5 years ago
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    ya but you understand this. I son't understand any of it. I just started in Jan to learn this junk

  60. anonymous
    • 5 years ago
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    ya, this si easy. but im doing precal, and ap microecon, and ap Human Geogarohy, and ap bio

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