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Thread: Simultaneous equation

  1. #1
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    Simultaneous equation

    Hello, could somebody solve this to find the values for P1 and P2 for me and show how they have worked it out I am struggling a bit with it. Thanks

    2P1 - 5P2 = -6
    -P1 + 3P2 = 4
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  2. #2
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    Re: Simultaneous equation

    Use "easier" variables:
    2a - 5b = -6 [1]
    -a + 3b = 4 [2]

    Multiply [2] by 2:
    -2a + 6b = 8 [2]

    Continue by adding the 2 equations...
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  3. #3
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    Re: Simultaneous equation

    Quote Originally Posted by davefrick1 View Post
    Hello, could somebody solve this to find the values for P1 and P2 for me and show how they have worked it out I am struggling a bit with it. Thanks

    2P1 - 5P2 = -6
    -P1 + 3P2 = 4
    Using your variables, Multiply the second equation by 2 to get
    -2P1+ 6P2= 8 and add the first equation
    2P1- 5P2= -6

    P2= 2. With P2= 2, the second equation is -P1+ 3(2)= -P1+ 6= 4. So -P1= 4- 6= -2 and P1= 2.
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  4. #4
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    Re: Simultaneous equation

    Thank you that was very helpful
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  5. #5
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    Re: Simultaneous equation

    Another way: from -P_1+ 3P_2= 4 adding P_1 to both sides gives 3P_2= 4+ P_1 and then subtracting 4 from both sides gives 3P_2- 4= P_1. Now, we can replace P_1 with 3P_2- 4 in 2P_1- 5P_2=- 6: 2(3P_2- 4)- 5P_2= 6P_2- 8- 5P_2= P_2- 8= -6 so P_2= 8- 6= 2. Then P_1= 3P_2- 4= 3(2)- 4= 6- 4= 2.
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