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Topic: Simplifying Algebraic Expressions with Subtracted Expressions
Replies: 67   Last Post: Nov 25, 2013 12:57 PM

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 Robert Hansen Posts: 11,345 From: Florida Registered: 6/22/09
Re: Simplifying Algebraic Expressions with Subtracted Expressions
Posted: Nov 11, 2013 10:33 PM

I was working with my son a couple days ago with several expressions involving parenthesis. I remembered a little over a year ago when he came home one day and told me that the teacher had taught them about parenthesis. I asked "So what do parenthesis do?" and he replied "You do the math inside the parenthesis first." If you keep at it, starting with that simple definition, the rest all works out. Take something simpler first, like "1 - (5 - 3)". If you do enough problems of that sort the student will get the underlying mechanism of these operations in combination and you will not have to teach any of these properties explicitly (by rote) nor will you have to explain them. Instead, you will supply names for things they now already know and help them organize and formalize their thoughts.

I do miss that day when he came home and told me "You do the math inside the parenthesis first." I sometimes wonder who is getting the better deal here. Me teaching him math or him allowing me to learn it all over again.

In any event, stop thinking in terms of properties and methods. Think in terms of familiarity with the operations, grouping and the effect that oder has on the result. Familiarity is the key.

Bob Hansen

On Nov 11, 2013, at 9:21 PM, MVTutor <johnstearns611@yahoo.com> wrote:

> How would you advise students in the example "1-(x+2-3)"?
> Can I tell them to drop the parentheses and reverse the signs of each term?
> Is the explanation that if we change the subtraction to an addition we can use the associative property of addition?
> Are there alternative methods?
> I've seen one book that suggests solving it as follows:
> 1-(x+2-3) => 1+ -1(x+2-3)=> then solve -1(x+2-3)
> - -1(x)+-1(2)- (-1)(-3)
> but this seems a bit confusing to me.
> Any suggestions?
> Thanks, --John

Date Subject Author
11/11/13 MVTutor
11/11/13 Robert Hansen
11/12/13 Bishop, Wayne
11/12/13 MVTutor
11/13/13 Jonathan J. Crabtree
11/13/13 Bishop, Wayne
11/14/13 Joe Niederberger
11/14/13 Robert Hansen
11/14/13 Joe Niederberger
11/14/13 Robert Hansen
11/14/13 Joe Niederberger
11/14/13 Robert Hansen
11/14/13 Louis Talman
11/14/13 Joe Niederberger
11/14/13 Robert Hansen
11/14/13 Robert Hansen
11/16/13 Bishop, Wayne
11/16/13 Robert Hansen
11/14/13 Joe Niederberger
11/14/13 Robert Hansen
11/16/13 Bishop, Wayne
11/14/13 Pam
11/15/13 Robert Hansen
11/15/13 Joe Niederberger
11/15/13 Robert Hansen
11/15/13 Joe Niederberger
11/15/13 Joe Niederberger
11/15/13 Joe Niederberger
11/15/13 Robert Hansen
11/16/13 Bishop, Wayne
11/16/13 Robert Hansen
11/17/13 Bishop, Wayne
11/17/13 Robert Hansen
11/17/13 Bishop, Wayne
11/15/13 Joe Niederberger
11/15/13 Robert Hansen
11/15/13 Pam
11/15/13 Robert Hansen
11/15/13 Pam
11/16/13 Robert Hansen
11/16/13 Robert Hansen
11/16/13 Joe Niederberger
11/16/13 Robert Hansen
11/18/13 Louis Talman
11/21/13 Robert Hansen
11/21/13 Louis Talman
11/16/13 Pam
11/16/13 Robert Hansen
11/16/13 Pam
11/16/13 Robert Hansen
11/18/13 GS Chandy
11/17/13 GS Chandy
11/17/13 Pam
11/17/13 Robert Hansen
11/17/13 Pam
11/17/13 Robert Hansen
11/17/13 Pam
11/18/13 Robert Hansen
11/18/13 Robert Hansen
11/18/13 Pam
11/18/13 Robert Hansen
11/25/13 Bishop, Wayne
11/25/13 Robert Hansen
11/22/13 Joe Niederberger
11/25/13 Bishop, Wayne
11/23/13 GS Chandy
11/24/13 Robert Hansen
11/25/13 Bishop, Wayne