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Markd Group Title

using a=-1, b=2, c=-3, d=4 show an expression using only those 4 letters that equals 22, 28 and 29. You can use square roots and exponents.

  • one year ago
  • one year ago

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  1. theEric Group Title
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    Your teacher is maniacal, in that you can't use algebra to just solve or anything.... You could create a program to find the results of many, many combinations. But for now we'll just have to logic it out. Does that sound good? Or are you in a high level class that I'm not understanding?

    • one year ago
  2. theEric Group Title
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    Can we use addition and subtraction?

    • one year ago
  3. Markd Group Title
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    You can use addition or subtraction. it 7th grade math

    • one year ago
  4. theEric Group Title
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    like \[z+z+z-y\]

    • one year ago
  5. theEric Group Title
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    Okay, that makes this easier!

    • one year ago
  6. Markd Group Title
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    example: (b^d)-(a+c) = 20

    • one year ago
  7. theEric Group Title
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    Okay! Well I was going to be cheap, since you can really count with the -1. I mean, that's a. And -a = 1. So -a = 1, -a + -a =2, -a + -a + -a = 3, etc.

    • one year ago
  8. theEric Group Title
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    That's probably not the purpose of the assignment, though. Huh?

    • one year ago
  9. Markd Group Title
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    no, you can only use each number one time in each expression.

    • one year ago
  10. theEric Group Title
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    Oh! Tricky! :) A challenge!

    • one year ago
  11. Markd Group Title
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    another example -(d-c)^b/a = 14 note ^ means to the power

    • one year ago
  12. theEric Group Title
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    Understood, thank you!

    • one year ago
  13. theEric Group Title
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    And numbers are not allowed, right?

    • one year ago
  14. Markd Group Title
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    we had to come up with an expression for every day of the month of October. I got 28 of the 31 done and these last three have me stumped!

    • one year ago
  15. theEric Group Title
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    Oh wow!!

    • one year ago
  16. Markd Group Title
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    you can use the numbers -1, 2, -3 and 4 instead of the letters if you want to. you find the expression and the least I can do is translate it! lol

    • one year ago
  17. theEric Group Title
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    Haha, okay.

    • one year ago
  18. Markd Group Title
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    is this something you think you can help me with?

    • one year ago
  19. theEric Group Title
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    Haha, I'm working on it! Logically, it stinks that you can't use any more than once, but it's great that you can switch the sign of any of them by making them negative.

    • one year ago
  20. theEric Group Title
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    I need a break from some math homework of my own that's not due for a little while, so I'll work these out with you.

    • one year ago
  21. Markd Group Title
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    I kind of added the "switch the sign" rule myself. Im not sure that thats allowed but its the only way I could figure out some of them.

    • one year ago
  22. theEric Group Title
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    I see. This sounds like a tough math assignment.

    • one year ago
  23. Markd Group Title
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    Are you in high school or college?

    • one year ago
  24. theEric Group Title
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    25 = (b-c) ^ (d-a), so you can have that in case you're other one involved just making a variable negative. I'm in college. My brain is currently deflated... I was working on homework in a subject called, "Introduction to Mathematical Proofs". The premise of the class is that, if you know some basic math definitions, you can establish true statements. Everything in math is defined, very specifically. Example, even numbers. They have a definition. Pretty much, an even number is a multiple of 2. Then, (I won't bother you with details) and example of a truth you can mathematically prove is that the product of any two even numbers will be even. It's sort of common sense, but the course demands us to be very specific. Algebra makes it easier. Back to the 22, 28, and 29!

    • one year ago
  25. Markd Group Title
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    Sounds hard! But believe it our not i did understand what you just said!

    • one year ago
  26. theEric Group Title
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    Sweet! I believe it! The stuff you're working on is hard too!

    • one year ago
  27. Markd Group Title
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    Are you sure 25 is correct? (2--3)^4--1= 5^5 correct? isnt that 3,125?

    • one year ago
  28. Markd Group Title
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    am I wrong on my thinking?

    • one year ago
  29. theEric Group Title
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    Hahaha!! Umm...... Let's go with (2--3) * (4--1)

    • one year ago
  30. Markd Group Title
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    that works!

    • one year ago
  31. theEric Group Title
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    Haha, I did say my brain was deflated! Thank you for catching me, and I'm sorry I told you something incorrect!

    • one year ago
  32. Markd Group Title
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    its OK. your thinking was right

    • one year ago
  33. theEric Group Title
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    Haha, thank you.

    • one year ago
  34. Markd Group Title
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    this is kind of like the show "Are you smarter than a 6th grader"

    • one year ago
  35. theEric Group Title
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    Hahaha!! You are totally right!

    • one year ago
  36. theEric Group Title
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    Great comparison...

    • one year ago
  37. Markd Group Title
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    OK, we could use absolute value on 5 of these and I just found answers to 2 two of the ones I had already done without using absolute values. So I have 2 more I can use now. So if it helps you try using absolure values if you need to.

    • one year ago
  38. Markd Group Title
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    does that make sence?

    • one year ago
  39. Markd Group Title
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    example: |d|+|c|+|a|*b=16

    • one year ago
  40. theEric Group Title
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    Alright! Your assignment makes a point that there are a limited amount of absolute values. |a| = -a. Does your assignment want to limit that -a thing too? It's like (-1)a, which is involving another number... Maybe we can change them later, if you want!

    • one year ago
  41. Markd Group Title
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    of the 31 expression I can only have 5 that use absolute values. I have 2 more absolute values left to use. Keep in mind you can use as many absolute values you want to in each expression.

    • one year ago
  42. theEric Group Title
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    But then we can use -2 or -4 in multiplication so easily... They'd have to be multiplied by a = -1. Addition is fine. x + (-b) = x - b. Subtraction is also fine. x - (-b) = x + b

    • one year ago
  43. Markd Group Title
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    yes, I believe thate right. Im not sure I understood that.

    • one year ago
  44. theEric Group Title
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    Okay! I'm going to go to a store quickly. I'll be back.

    • one year ago
  45. Markd Group Title
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    ok

    • one year ago
  46. theEric Group Title
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    Well you weren't sure if we could just use -a, or -c. If we could, then why put a limit on how many absolute values we use? Since we can get the same result with -a as |a|, why put a limit on how many times we can use |a|, but not limit -a. I think -a would not count because you get -a by multiplying -1 and a. Since -1 is a number, it wouldn't be allowed.

    • one year ago
  47. Markd Group Title
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    i see your point.

    • one year ago
  48. theEric Group Title
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    -1, 2, -3, 4 Results by multiplying two different variables -2 = 2 * -1 3 = -3 * -1 -4 = 4 * -1 -6 = -3 * 2 8 = 4 * 2 -12 = 4 * -3 Results by using powers, but not absoute value 1 = 2 ^ -1 -1 = -3 ^ -1 1 = 4 ^ -1 16 = 4 ^ 2 81 = 4 ^ -3 Results by using powers, and possiblly absolute value 1 = 1 ^ 2 1 = 1 ^ 3 1 = 1 ^ 4 8 = 2 ^ 3 16 = 2 ^ 4 81 = 3 ^ 4

    • one year ago
  49. theEric Group Title
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    Haha, I don't know if that is helpful or not. But those are numbers you might recognize that you need. They are the result of taking two variables and doing something to them. I think I overcomplicated it :P

    • one year ago
  50. Markd Group Title
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    no, i follow you

    • one year ago
  51. theEric Group Title
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    Haha, alright.

    • one year ago
  52. theEric Group Title
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    Some of that is wrong, sorry.. I wrote a program to do that for me, so I wrote it wrong. 81 doesn't equal 4^-3

    • one year ago
  53. Markd Group Title
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    is 2^-1=-1 why wouldn't it be -2? Is that a rule?

    • one year ago
  54. theEric Group Title
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    Actually, ignore all of that! I made two mistakes: 1. Many of the second set are wrong because I switched.. like\[4^{-1}\neq1\]\[(-1)^4=1\] 2. Some are wrong otherwise, as my program used a program that rounded. I didn't know that it would. Also, I didn't include all possibilities. Here are the powers, if you use two variables and possibly absolute value: 1 = 1 ^ 2 1 = 1 ^ 3 1 = 1 ^ 4 2 = 2 ^ 1 8 = 2 ^ 3 16 = 2 ^ 4 3 = 3 ^ 1 9 = 3 ^ 2 81 = 3 ^ 4 4 = 4 ^ 1 16 = 4 ^ 2 64 = 4 ^ 3

    • one year ago
  55. theEric Group Title
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    And obviously we won't worry about anything to the first power.... So here I took that out. 1 = 1 ^ 2 1 = 1 ^ 3 1 = 1 ^ 4 8 = 2 ^ 3 16 = 2 ^ 4 9 = 3 ^ 2 81 = 3 ^ 4 16 = 4 ^ 2 64 = 4 ^ 3

    • one year ago
  56. theEric Group Title
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    Do you really want to know how a negative power works? It's not that hard, but it doesn't give us any extra help here. I will show you, if you want.

    • one year ago
  57. Markd Group Title
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    no, its OK. I will work off of what you just sent

    • one year ago
  58. theEric Group Title
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    Okay! I just thought those numbers could help us possibly.

    • one year ago
  59. Markd Group Title
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    Dont forget we can also use square roots

    • one year ago
  60. theEric Group Title
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    Right, thanks!

    • one year ago
  61. theEric Group Title
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    If only we could reuse some..

    • one year ago
  62. Markd Group Title
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    Would be nice...

    • one year ago
  63. theEric Group Title
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    \[\sqrt{4^{\left|-3\right|}}=\sqrt{64}=8\]\[\sqrt{\left|-3\right|^4}=\sqrt{81}=9\] More ways to get to 8 and 9, but maybe you already noticed! No use on focusing on what we can't do!

    • one year ago
  64. theEric Group Title
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    \[8=2*4\]\[9=(-1)(-3)^2=\left|-3\right|^2\]

    • one year ago
  65. Markd Group Title
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    can you think of anything that equals 20?

    • one year ago
  66. theEric Group Title
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    With or without absolute value?

    • one year ago
  67. Markd Group Title
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    (2^4)-(-1+-3) but that dont leave any numbers to use

    • one year ago
  68. Markd Group Title
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    either way

    • one year ago
  69. theEric Group Title
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    Right. I run into that problem too.

    • one year ago
  70. Markd Group Title
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    What state do you live in?

    • one year ago
  71. Markd Group Title
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    My brain is fried.

    • one year ago
  72. theEric Group Title
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    Understood. Maybe a break would help. And I hope you're not staying up too late! I don't know what time it would be where you are.

    • one year ago
  73. Markd Group Title
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    Im in Charlotte North Carolina. Its 11:40 here

    • one year ago
  74. theEric Group Title
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    Same here, in central Pennsylvania.

    • one year ago
  75. theEric Group Title
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    I'm not sure how dangerous it is to give town information over the internet. I'd presume it's not so bad. I never have though.

    • one year ago
  76. theEric Group Title
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    When is this project due?

    • one year ago
  77. Markd Group Title
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    Thank you so much for your help! It was a nice surprise to get your messages this morning.

    • one year ago
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