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Question -Substiution ALWAYS imagining invisible brackets in your head?

  1. Nov 28, 2008 #1
    Im in 2nd year of math now...so I know algebra but

    I was reading this from this website:

    "Substitution
    Every time we replace a part of an expression with a value or another expression, we are using the technique of Substitution. And, every time a substitution is performed, parentheses are used!"
    http://www.math.ohio-state.edu/~mcginnis/08Au%20M132N/Algebra%20Fundamentals.pdf [Broken]

    My question is...
    when you substitute into an expression...eg.

    e^x Sub in 2x+1 ...

    Maybe a bad eg since im typing it ...but if you were writing it on paper...

    I wouldnt even think about it...id just write e^(2x+1) ...(No Brackets)

    Or sub 2x for x in x+1 ...Id just write 2x+1


    or sqrt(x^2+y^2) ...evaulated at x=1=y Id just go sqrt(1^2+1^2)


    But do you ALWAYS imagine brackets in your head first...when youre doing these...

    Because im really worried that everyone else is doing this except me ..
     
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Nov 28, 2008 #2

    cristo

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    Staff Emeritus
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    I wouldn't write things the way you are writing. I would say "substitute x=2y+1 into exp(x)" otherwise you're bound to get confused.

    I think I would only "imagine brackets" when necessary. So, if all you're doing is adding things then it doesn't matter, but if you were to evaluate, say, "substitute x=1-y into 1-x" then ignoring the brackets will get you into trouble.
     
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