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Math Help - How to cross out long terms

  1. #1
    Member Jonboy's Avatar
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    How to cross out long terms

    How to cross out long terms?

    Like this: \frac{\rlap{---------}(x + 5)(x - 2)}{\rlap{---------}(x + 5)} = x - 2

    This is something I've been wanting to do again for a while but forgot. And I couldn't find it anywhere. Here's what I've found through experimentation.

    You use: \rlap {--}

    In front of the term where you want the slash to start.

    Then increase the "-" between the brackets until it's long enough.

    Is there an easier way to do this? I imagine so.
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  2. #2
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    I experimented with Jonboy's suggestion . . .


    It seems that "rlap" is an over-write command.


    \rlap{///}3x^2 . \Rightarrow\quad \rlap{///}3x^2

    \rlap{TRUE}false . \Rightarrow\quad \rlap{TRUE}false


    \rlap{|}X . \Rightarrow\quad \rlap{|}X

    \rlap{||}\:5T^2 . \Rightarrow\quad \rlap{||}\:5T^2

    I don't know why "|" produces a horizontal line.

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  3. #3
    Member Jonboy's Avatar
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    Thanks for the response Soroban! Very interesting findings.
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  4. #4
    Super Member wingless's Avatar
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    It would be much easier if we had the cancel package in LaTeX...
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  5. #5
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    Quote Originally Posted by Jonboy View Post
    How to cross out long terms?

    Like this: \frac{\rlap{---------}(x + 5)(x - 2)}{\rlap{---------}(x + 5)} = x - 2

    ...
    With Jonboy's method you can use different colours to cross out different terms.

    \frac{\bold{\rlap{{\color{red}====}}}(x + 5)(x - 2) \rlap{{\color{blue}---------}}(x + 7)}{\rlap{{\color{red}====}}(x + 5) \rlap{{\color{blue}---------}}(x + 7)} = \bold{x - 2}

    It would be nice and much more legible if the horizontal line could be printed in bold style. Unfortunately I didn't find the appropriate command . The \bold{..} obviously only works with numbers and letters.
    Last edited by earboth; July 31st 2008 at 01:51 AM.
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  6. #6
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    Quote Originally Posted by earboth View Post
    With Jonboy's method you can use different colours to cross out different terms.

    \frac{\bold{\rlap{{\color{red}====}}}(x + 5)(x - 2) \rlap{{\color{blue}---------}}(x + 7)}{\rlap{{\color{red}====}}(x + 5) \rlap{{\color{blue}---------}}(x + 7)} = \bold{x - 2}

    It would be nice and much more legible if the horizontal line could be printed in bold style. Unfortunately I didn't find the appropriate command . The \bold{..} obviously only works with numbers and letters.
    Using \vrule, you can create lines of any height, depth and width that you want. For example, \frac{(\rlap{\color{red}\vrule height3.5pt depth-2pt width2.3em}x + 5)(x - 2) (\rlap{\color{blue}\vrule height3.5pt depth-2pt width2.3em}x + 7)}{(\rlap{\color{red}\vrule height3.5pt depth-2pt width2.3em}x + 5) (\rlap{\color{blue}\vrule height3.5pt depth-2pt width2.3em}x + 7)} = x - 2 comes from this code:

    Code:
    \frac{(\rlap{\color{red}\vrule height3.5pt depth-2pt width2.3em}
    x + 5)(x - 2) (\rlap{\color{blue}\vrule height3.5pt depth-2pt width2.3em}
    x + 7)}{(\rlap{\color{red}\vrule height3.5pt depth-2pt width2.3em}
    x + 5) (\rlap{\color{blue}\vrule height3.5pt depth-2pt width2.3em}
    x + 7)} = x - 2
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