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Math Help - Quick question regarding partial decomposition.

  1. #1
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    Quick question regarding partial decomposition.

    I was just wondering about the steps that are described here but not shown. I don't see what they mean by subtracting equation 3 from equation 1 and using that in equation 2. Could someone show me the steps that were left out?

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  2. #2
    Super Member 11rdc11's Avatar
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    They used elimanation to get rid of A and then use elimanation again to get rid of B or C
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  3. #3
    Moo
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    Hello,

    \begin{aligned} (1) ~ & 1 &=& {\color{red}\boxed{A}} &+&3B&&& \\<br />
(2) ~ &1&=&&&-B&+&3C \\<br />
(3) ~ &-2&=&{\color{red}\boxed{A}}&&&-&C \end{aligned}

    The red boxes tell us to substract (1) from (3) or (3) from (1).
    This gives 1-(-2)=A+3B-(A-C) \implies 3=3B+C \implies C=3-3B

    Substitute it in (2).
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  4. #4
    Super Member 11rdc11's Avatar
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    Quote Originally Posted by Moo View Post
    Hello,

    \begin{aligned} (1) ~ & 1 &=& {\color{red}\boxed{A}} &+&3B&&& \\<br />
(2) ~ &1&=&&&-B&+&3C \\<br />
(3) ~ &-2&=&{\color{red}\boxed{A}}&&&-&C \end{aligned}

    The red boxes tell us to substract (1) from (3) or (3) from (1).
    This gives 1-(-2)=A+3B-(A-C) \implies 3=3B+C \implies C=3-3B

    Substitute it in (2).
    I tried so hard to get mine to look like that but couldn't. I just gave up and gave an explanation lol
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  5. #5
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    Quote Originally Posted by redman223 View Post
    I was just wondering about the steps that are described here but not shown. I don't see what they mean by subtracting equation 3 from equation 1 and using that in equation 2. Could someone show me the steps that were left out?

    Hey, are you in Mrs. Duncan's class? haha, I'm in here 8AM class. That is from elluminate?
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  6. #6
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    Lol, yeah I am in the 2:00 class. Thanks for all the replies.
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