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Math Help - [SOLVED] Equation Help

  1. #1
    Newbie
    Joined
    Jan 2008
    Posts
    10

    [SOLVED] Equation Help

    3x - 5(-2x-8) + 4 = 2 - (x-4)

    I got 3, back of the book says it's -19 over 7

    Got it:

    3X - 5 (-2X-8) + 4 = 2 - (X-4)

    3X + 10X + 40 + 4 = 2 - (X-4)

    3X + 10X + 40 + 4 = 2 - X + 4

    |
    | Combine terms of X
    13X + 40 + 4 = 2 - X + 4

    |
    | Combine constants.
    13X + 44 = 2 - X + 4

    |
    | Combine constants.
    13X + 44 = 6 - X

    | Sort terms in decreasing powers.
    13X + X = - 44 + 6

    |
    | Combine terms of X
    14X = - 44 + 6

    |
    | Combine constants.
    14X = - 38

    |
    | Next divide by 14, the coefficient of X.

    7X = - 19

    | Multiply by 1 to clear decimals.

    - 19
    X = + ______
    7

    |
    | Check solutions by substituting each one in the original equation.
    |
    | CHECKING SOLUTION #1: X = -2.71429
    3X - 5 (-2X-8) + 4 = 2 - (X-4)

    - 8.14286 + 5(2.57143) + 4 = 2 - (X-4)

    - 8.14286 + 12.8571 + 4 = 2 + 6.71429

    4.71429 + 4 = 2 + 6.71429

    8.71429 = 2 + 6.71429

    8.71429 = 8.71429

    | Both sides of equation are equal.
    | X = -2.71429 solution is verified.
    | Check successful
    | The solution set is valid.

    ***** Problem Summary *****
    Problem: Solve
    |
    | 3X - 5 (-2X-8) + 4 = 2 - (X-4)
    |

    Solution

    |
    | Solution: X = -2.71429
    |
    ***** End of Problem *****
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  2. #2
    Senior Member
    Joined
    Feb 2008
    Posts
    297
    Okay, here's my way of working it out:

    3x - 5(-2x-8) + 4 = 2 - (x-4)
    3x+10x+40+4=2-x+4
    13x + 44 = 6 - x
    13x+44+x=6
    14x=6-44
    14x=-38
    x=-38/14
    Therefore:
    x=-19/7
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