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Math Help - Grade 7 Algebra

  1. #1
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    Grade 7 Algebra

    I need help here is the question i need to find out how to do this step to step
    3A+ 4b-2c-4A+5B-1C
    A=2
    B=-1
    c=4
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  2. #2
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    Quote Originally Posted by MoneyMaker View Post
    I need help here is the question i need to find out how to do this step to step
    3A+ 4b-2c-4A+5B-1C
    A=2
    B=-1
    c=4
    I have spread out the expression to make it easier for you.

    You have: 3A\quad+\quad 4B\quad  - \quad 2C \quad -\quad  4A \quad + \quad 5B \quad - \quad 1C


    Substitute: 3(2)\quad+\quad 4(-1)\quad  - \quad 2(4) \quad -\quad  4(2) \quad + \quad 5(-1) \quad - \quad 1(4)


    Solve: 6\quad+\quad -4\quad  - \quad 8 \quad -\quad  8 \quad + \quad -5 \quad - \quad 4


    Adding a negative number means you subtract: 6\quad-\quad 4\quad  - \quad 8 \quad -\quad  8 \quad - \quad 5 \quad - \quad 4

    And I'm sure you can do it from there.
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  3. #3
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    Quote Originally Posted by MoneyMaker View Post
    I need help here is the question i need to find out how to do this step to step
    3A+ 4b-2c-4A+5B-1C
    A=2
    B=-1
    c=4
    I guess you mean all upper quotes

    3A+ 4B-2C-4A+5B-1C = (3*2) + [4*(-1) ] - (2*4) - (4*2) + [ 5*(-1) ] - (1*4)

    = 6 + (-4) - 8 -8 + (-5) - 4

    = 6 - 4 - 8 - 8 - 5 - 4

    = 6 - 29

    = -23

    remember that
    +ve * +ve = +ve

    +ve * -ve = -ve

    -ve * -ve = +ve



    see this page for precedence of operations

    order of performing mathematical operations
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  4. #4
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    first you collect "like terms", not sure if thats a term you have used but it means adding up whats "like" before subing numbers in so

    3A + 4B - 2C - 4A +5B - C becomes
    -1A +9B -3C ( as you have added all the A's together and so on.)

    then you sub in the numbers so,

    -1(2) + 9(-1) -3(4) = -2-9-12 = -23
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