Results 1 to 7 of 7

Math Help - whats the right answer

  1. #1
    Junior Member
    Joined
    Jan 2009
    From
    in space
    Posts
    60

    whats the right answer

    4x + 12 = 3(4 - X)
    well 4x + 12 = 12 - 3x
    4x + 12 -12 =12 - 3x -12
    = 4x -12 = 12 -12 -9
    = -8x -9
    =8x/8 -9/8 = - 1 1/8 book says answer is 0 . not thinking right can someone help.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Rhymes with Orange Chris L T521's Avatar
    Joined
    May 2008
    From
    Santa Cruz, CA
    Posts
    2,844
    Thanks
    3
    Quote Originally Posted by Leona_Marie View Post
    4x + 12 = 3(4 - X)
    well 4x + 12 = 12 - 3x
    4x + 12 -12 =12 - 3x -12
    = 4x -12 = 12 -12 -9
    = -8x -9
    =8x/8 -9/8 = - 1 1/8 book says answer is 0 . not thinking right can someone help.
    The line in red is where you started to go wrong...

    You have 4x+12-12=12-3x-12\implies 4x+(12-12)=-3x+(12-12)

    Note that I put some terms in parenthesis to make the next step in the process easier to see. Can you continue?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Jan 2009
    From
    in space
    Posts
    60
    Quote Originally Posted by Chris L T521 View Post
    The line in red is where you started to go wrong...

    You have 4x+12-12=12-3x-12\implies 4x+(12-12)=-3x+(12-12)

    Note that I put some terms in parenthesis to make the next step in the process easier to see. Can you continue?
    switching 12 around doesnt make the answer 0
    4x +12 -12 = -3x + 12 -12
    = 4x = -3x
    =4x +3x = -3x + 3x
    =7x not 0 plus the only rule is that whatever you do to the left you have to do to the right. the right in this equation is -3x so -3x -12, which is 3x -12 ,would be -9
    Follow Math Help Forum on Facebook and Google+

  4. #4
    A riddle wrapped in an enigma
    masters's Avatar
    Joined
    Jan 2008
    From
    Big Stone Gap, Virginia
    Posts
    2,551
    Thanks
    12
    Awards
    1
    Quote Originally Posted by Chris L T521 View Post
    The line in red is where you started to go wrong...

    You have 4x+12-12=12-3x-12\implies 4x+(12-12)=-3x+(12-12)

    Note that I put some terms in parenthesis to make the next step in the process easier to see. Can you continue?
    Quote Originally Posted by Leona_Marie View Post
    switching 12 around doesnt make the answer 0
    4x +12 -12 = -3x + 12 -12
    = 4x = -3x
    =4x +3x = -3x + 3x
    =7x not 0 plus the only rule is that whatever you do to the left you have to do to the right. the right in this equation is -3x so -3x -12, which is 3x -12 ,would be -9
    Go back and look at what Chris has shown you.

    4x+12-12=12-3x-12\implies 4x+(12-12)=-3x+(12-12)

    4x+0=-3x+0

    4x=-3x

    4x+3x=0

    7x=0

    x=0
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Jan 2009
    From
    in space
    Posts
    60
    masters , please explain to me how 7x = 0 or x = 0 the only thing I would know how to do is to devide 7x/7 0/7 = 0 ? plus Ive never seen wher you can swap + -3x + 12 or visa versa is this the case or am I missing something again. in other words the question was written out12 -3x so shouldnt the number come off the right. I think I just got it please verify.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Member TheMasterMind's Avatar
    Joined
    Dec 2008
    Posts
    155
    Quote Originally Posted by Leona_Marie View Post
    4x + 12 = 3(4 - X)
    well 4x + 12 = 12 - 3x
    4x + 12 -12 =12 - 3x -12
    = 4x -12 = 12 -12 -9
    = -8x -9
    =8x/8 -9/8 = - 1 1/8 book says answer is 0 . not thinking right can someone help.
    4x+12=12-3x

    4x+3x=12-12

    7x=0

    x=0

    expand,collect, and you're done!
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Member TheMasterMind's Avatar
    Joined
    Dec 2008
    Posts
    155
    Quote Originally Posted by Leona_Marie View Post
    masters , please explain to me how 7x = 0 or x = 0 the only thing I would know how to do is to devide 7x/7 0/7 = 0 ? plus Ive never seen wher you can swap + -3x + 12 or visa versa is this the case or am I missing something again. in other words the question was written out12 -3x so shouldnt the number come off the right. I think I just got it please verify.
    yes 0/7 is what masters did.. which = 0 and you can always swap to other sides of the equation to collect like terms(as long as you change the sign)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. ok whats wrong/right about this answer?
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: August 12th 2010, 10:03 PM
  2. Whats the Spread?
    Posted in the Algebra Forum
    Replies: 1
    Last Post: May 10th 2010, 07:16 PM
  3. whats d^2y/dx^2?
    Posted in the Calculus Forum
    Replies: 3
    Last Post: January 2nd 2010, 04:14 PM
  4. Okay whats going on here....
    Posted in the Calculus Forum
    Replies: 6
    Last Post: May 29th 2008, 08:02 PM
  5. Whats a BASE???
    Posted in the Algebra Forum
    Replies: 8
    Last Post: April 4th 2008, 01:25 PM

Search Tags


/mathhelpforum @mathhelpforum