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anonymous

  • 5 years ago

12x-3(2x+7)=-45 could someone walk me through this

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  1. anonymous
    • 5 years ago
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    You want to try and get the x on one side and the anything else on the other.

  2. anonymous
    • 5 years ago
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    So I would start with distributing the 3 through that quantity...

  3. anonymous
    • 5 years ago
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    Okay, so we start off by distrubiting the '-3' to the (2x+7). -3*2x = -6x; -3 * 7 = -21 This leaves us with: 12x -6x -21 = -45 We group like terms: ie. 12x-6x = 6x; We're left with 6x-21=-45, so lets add 21 to both sides. 6x-21+21 = -45+21 This simplifies to: 6x = -24; we now divide by 6 x = -4. Done!

  4. anonymous
    • 5 years ago
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    -3(2x+4)=5(3-2x) mind helping me again

  5. anonymous
    • 5 years ago
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    tlk to me like im a 5 yr old lol

  6. anonymous
    • 5 years ago
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    Without just giving you the answer, it's always best to try yourself. That's the way you learn. So we need to distribute again, i.e multiply the -3 through and the 5 through.

  7. anonymous
    • 5 years ago
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    ok -6x+4=15-10x

  8. anonymous
    • 5 years ago
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    first step right?

  9. anonymous
    • 5 years ago
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    Not quite. I think you had the right process because you used it on the right side correct. You forgot to multiply the 4 by -3.

  10. anonymous
    • 5 years ago
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    wait

  11. anonymous
    • 5 years ago
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    i just caught it

  12. anonymous
    • 5 years ago
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    so -6x+12=15-10x

  13. anonymous
    • 5 years ago
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    Minus 12 :) So -6x-12=15-10x

  14. anonymous
    • 5 years ago
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    see this where i get confused when do i need to change signs

  15. anonymous
    • 5 years ago
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    Ok since the first time you are multiplying by -3 anything positive becomes negative.

  16. anonymous
    • 5 years ago
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    when i need to change from addition to sub

  17. anonymous
    • 5 years ago
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    i understand that but like on a 2 or 3 step prob when do i change the operation

  18. anonymous
    • 5 years ago
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    I'm not quite sure what you're asking. I would need an example...

  19. anonymous
    • 5 years ago
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    im really pretty intelligent i promise....lol

  20. anonymous
    • 5 years ago
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    let me find an example

  21. anonymous
    • 5 years ago
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    Math is not everyone's thing. I just happen to be good at it. :) Music, on the other hand, I only listen to it.

  22. anonymous
    • 5 years ago
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    ok

  23. anonymous
    • 5 years ago
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    Here's a few more examples of "changing the sign". I'm not sure I understand what you're asking so maybe you will see the pattern yourself. 3(7x+2) = 21x+6 --- A positive * a positive is a positive. -3(3x+2) = -9x-6 --- A negative number * a positive is a negative. 5(-2x-1) = -10x - 5 --- A positive number * a negative is a negative. -7(8x-4) = -56x + 28 --- The first part is a negative * a positive = negative, but the second is a negative times a negative which is a positive. Can you try simplifying: -3(-4x+7) = ??? for me?

  24. anonymous
    • 5 years ago
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    6x+9-4x=3x+11

  25. anonymous
    • 5 years ago
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    12x+-21?

  26. anonymous
    • 5 years ago
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    Yep! If it helps you to think of it as "Twelve x plus negative 21" then by all means leave it like that.

  27. anonymous
    • 5 years ago
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    As for the problem you posted above, first, let's simplify the left side by adding like terms. Then try adding something to both sides to get the x's on one side. Then add another something to get the "numbers" on the other side. Then divide by the number in front of the x to get your final answer.

  28. anonymous
    • 5 years ago
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    10x+9=3x+11 or 13x=20 cani combine both sides of the = sign at once?

  29. anonymous
    • 5 years ago
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    wait i just read what u wrote

  30. anonymous
    • 5 years ago
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    6x+9-4x=3x+11 5x+9=11?

  31. anonymous
    • 5 years ago
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    You can if you can keep track in it -- with no offense met, I'd practice doing them individually for at least a week of classes. When you've got it down pat feel free to add on steps in your head. Eventually you'll reach a point where you can solve 6x+9-4x=3x+11 all in your head. You made a mistake in your answer though: Left hand side first: 6x+9-4x = 2x + 9; You added 4x in an attempt to kill the -4x, but if you're going to do that you must do that to both sides. It is far easier just to do "6x-4x = 2x" Now the left side: Oh wait! It's already done! "2x+9" So we have 2x+9 = 3x +11; Subtract 2x from each side ---> 2x+9-2x = 3x-2x+11 ----> 9 = x+11 Now lets subtract 11 from each side leaving: -2 = x; You can then check the answer

  32. anonymous
    • 5 years ago
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    Are you able to follow what I did? If you'd like I can give another example, but can you explain your thought process for me as you solve it?

  33. anonymous
    • 5 years ago
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    Here's a problem I just made up if you'd like to try again: -5(3x+1) = 16x-3

  34. anonymous
    • 5 years ago
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    -15x+1=16x-3

  35. anonymous
    • 5 years ago
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    Make sure to distrubute the "-5" to everything in the parantheses.

  36. anonymous
    • 5 years ago
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    -15+-1=16x-3

  37. anonymous
    • 5 years ago
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    so combine right

  38. anonymous
    • 5 years ago
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    so when one distrubutes you take the number outside of the parentheses and multiply it by each of the (inside terms). so you are doing: -5 * 3x; AND -5 * 1; so we have -15x -5 (or in your preffered notation: -15x + -5)

  39. anonymous
    • 5 years ago
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    We can come back to distrubution later if you'd like: -15x + -5 = 16x + -3 is where we can pick this up again. Do this out but tell me in words what you're doing as well please. I want to see what you're thinking haha. Cheers for sticking with this btw.

  40. anonymous
    • 5 years ago
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    then we combine the x's together so mobve the smaller x to both sides?

  41. anonymous
    • 5 years ago
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    trust me id rather b watching family guy,,,lol

  42. anonymous
    • 5 years ago
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    Yep. So yeah, add the Opposite of the smaller x value to both sides.

  43. anonymous
    • 5 years ago
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    -15x+-5=16x+-3 -15x+-5=-15x+-3 x=-5=1x+-3?

  44. anonymous
    • 5 years ago
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    Also, I was asleep when making this example: The end result will be a fraction, my mistake.

  45. anonymous
    • 5 years ago
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    no worries

  46. anonymous
    • 5 years ago
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    Errr, okay, so explaint to me how you went from: -15x+-5=16x+-3 to -15x+-5=-15x+-3

  47. anonymous
    • 5 years ago
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    wait wait sorry

  48. anonymous
    • 5 years ago
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    As a reminder, our first goal is to get rid of the x's from the left hand side. The way we do this is by adding the opposite of them to it. Anything + the opposite of anything = 0; Anything + -Anything = 0.

  49. anonymous
    • 5 years ago
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    (and when we add anything (completely new) to one side, we must do it to the other).

  50. anonymous
    • 5 years ago
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    -15x+-5=16x+-3 15x=-15=16x+-3....so 20=16x+-3...not done but thats how i do the first side right

  51. anonymous
    • 5 years ago
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    u with me or u fall asleep again

  52. anonymous
    • 5 years ago
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    I'm not sure what you did there? Both sides are (by themselves) as simplified as you can get them without adding completely new things to the equation. Let's do this: 3x+2 = 4x+1 Each side is as simplified as possible: Let's get the x's over to the right. If I add -3x to both sides (which is the opposite of the the left hand side term), we get: 3x-3x+2 = 4x+1-3x ---> 3 = 4x+1. Now using this example, try doing -15x + -5=16x + -3 again. Also, remember you can not add a variable, the "x's" to the constants "the numbers".

  53. anonymous
    • 5 years ago
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    Now using this example as a refrence, try doing* (correction to the above)

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