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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:

    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 M132N/Algebra Fundamentals.pdf

    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 ..
  2. jcsd
  3. Nov 28, 2008 #2


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    Staff Emeritus
    Science Advisor

    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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