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Math Help - I need some clarification

  1. #1
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    I need some clarification

    my prof did this in his lecture:

    \frac{A(x-1)+B(x+2)}{(x+2)(x-1)}

    = \frac{x(A+B)+2(A-B)}{(x+2)(x-1)}

    Can anyone tell me what he did?
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  2. #2
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    Quote Originally Posted by jschlarb View Post
    my prof did this in his lecture:

    \frac{A(x-1)+B(x+2)}{(x+2)(x-1)}

    = \frac{x(A+B)+2(A-B)}{(x+2)(x-1)}

    Can anyone tell me what he did?
    \frac{A(x-1)+B(x+2)}{(x+2)(x-1)}=\frac{Ax-A+Bx+2B}{(x+2)(x-1)}= \frac{Ax+Bx+2B-A}{(x+2)(x-1)}


    = \frac{x(A+B)+(-A+2B)}{(x+2)(x-1)}

    I don't think that they are equal
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  3. #3
    Moo
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    Hi again

    Quote Originally Posted by jschlarb View Post
    my prof did this in his lecture:

    \frac{A(x-1)+B(x+2)}{(x+2)(x-1)}
    =\frac{Ax-A+Bx+2B}{(x+2)(x-1)}, by expanding.

    =\frac{Ax+Bx-A+2B}{(x+2)(x-1)}, by rearranging.

    = \frac{x(A+B)+({\color{red}2B-A})}{(x+2)(x-1)}

    Can anyone tell me what he did?
    There's something wrong in what you've written ~
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  4. #4
    Bar0n janvdl's Avatar
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    Quote Originally Posted by jschlarb View Post
    my prof did this in his lecture:

    \frac{A(x-1)+B(x+2)}{(x+2)(x-1)}

    = \frac{x(A+B)+2(A-B)}{(x+2)(x-1)}

    Can anyone tell me what he did?
    \frac{Ax-A+Bx+2B}{(x+2)(x-1)}

    \frac{Ax+Bx+2B - A}{(x+2)(x-1)}

    \frac{x(A+B)+ (2B - A)}{(x+2)(x-1)}

    That's as far as I get though...
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  5. #5
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    Smile

    Quote Originally Posted by Moo View Post
    Hi again



    =\frac{Ax-A+Bx+2B}{(x+2)(x-1)}, by expanding.

    =\frac{Ax+Bx-A+2B}{(x+2)(x-1)}, by rearranging.



    There's something wrong in what you've written ~

    That makes MUCH more sense. Thanks!
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