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anonymous

  • one year ago

Solve for x: -3|x + 7| = -12

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  1. anonymous
    • one year ago
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    Those lines just mean that the x+7 is positive so just think of it as parentheses. Distribute the -3 in (x+7).

  2. anonymous
    • one year ago
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    You should get -3x-21.

  3. anonymous
    • one year ago
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    -3x-21=-12

  4. anonymous
    • one year ago
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    Now try to solve this.

  5. anonymous
    • one year ago
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    It should be easier.

  6. anonymous
    • one year ago
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    x-18=-12

  7. anonymous
    • one year ago
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    right???

  8. anonymous
    • one year ago
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    Ya.

  9. anonymous
    • one year ago
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    x=6

  10. anonymous
    • one year ago
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    Then the answer would be x=6. But you aren't done there. When I told you that the absolute value is like parentheses, I was trying to not confuse you by saying that now you have to put a negative in front of the parentheses.

  11. anonymous
    • one year ago
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    Absolute values will always be positive and negative when it comes to equations.

  12. freckles
    • one year ago
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    you should get two answers first divide both sides by -3 |x+7|=4 you have to solve both equations below: x+7=4 or x+7=-4

  13. anonymous
    • one year ago
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    So now it should look like this(-3){-(x+7)}=-12

  14. anonymous
    • one year ago
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    then both by -11

  15. anonymous
    • one year ago
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    -3(-x-7)=-12 3x+21=-12 3x=-21-12 3x=-33 x=-11

  16. anonymous
    • one year ago
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    Yes that's the second answer.

  17. freckles
    • one year ago
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    x=6 gives a false equation -3|6+7|=-12 doesn't hold -3|13|=-12 -3(13)=-12 -39=-12 see this isn't the same thing on both sides so x=6 isn't a correct solution

  18. anonymous
    • one year ago
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    thxs i got my answers you guys are the best

  19. anonymous
    • one year ago
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    I don't think it's suppose to equal back to the problem @freckles. Look at this link. http://www.purplemath.com/modules/solveabs.htm

  20. anonymous
    • one year ago
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    And you're welcome!

  21. freckles
    • one year ago
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    yes it is in order for x=c to be a solution it must satisfy the equation

  22. anonymous
    • one year ago
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  23. freckles
    • one year ago
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    the first equation was just solved incorrectly

  24. anonymous
    • one year ago
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    When you plug in the 1st x of the equation from the picture. It doesn't equal 7. The second x does though.

  25. freckles
    • one year ago
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    -3(x+7)=-12 -3x-21=-12 add 21 on both sides -3x=-12+21 -3x=21-12 -3x=9 divide by -3 on both sides x=-3 as you see pluggin x=-3 into original this does satisfy initial equation -3|x+7|=-12 replace x with -3 -3|-3+7|=-12 -3|4|=-12 -3(4)=-12 -12=-12 this is a true equation so x=-3 is a solution just like x=-11 is also a solution since -3|x+7|=-12 pluggin in -11 for x -3|-11+7|=-12 -3|-4|=-12 -3(4)=-12 -12=-12 same thing on both sides the equation is true x=-11 is also a solution so the solution set is {-3,-11}

  26. freckles
    • one year ago
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    @200205650 you have to plug into the original equation

  27. anonymous
    • one year ago
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    Okay then never mind. You are right.

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