Associated Topics || Dr. Math Home || Search Dr. Math

### Variable Expressions with Parentheses

```
Date: 9/9/96 at 18:31:41
From: Anonymous
Subject: Variable Expressions with Parentheses

I can complete some problems like this, but often I come up with an
answer that is completly wrong and do not know why.  How do you solve:

2(x-1) - 3(2 - 3x) - (x + 1)

I can use the distributive property to simplify the first two parts of
the problem, but them I am lost...
```

```
Date: 9/9/96 at 19:17:40
From: Doctor Mike
Subject: Re: Variable Expressions with Parentheses

Hi,

The combination of the distributive property with minus signs often
causes a little bit of confusion.  First let's get to the place where
I think you are in the problem:

(2x-2) - (6-9x) - (x+1)

Notice that I have left it in the form of 3 expressions, where 2 of
them need to be subtracted.  The key thing to remember is to subtract
BOTH things inside the 2nd and 3rd expressions.  For instance, to
subtract 6-9x you have to subtract 6 and also subtract -9x.
The -(-9x) just becomes +9x.  So, after subtracting you get:

2x - 2 - 6 + 9x - x - 1

The next step is to combine like terms, that is, get all the x parts
together and get all the plain numbers together.  So,

10x - 9

I hope this helps.

-Doctor Mike,  The Math Forum
Check out our web site!  http://mathforum.org/dr.math/
```
Associated Topics:
Middle School Algebra

Search the Dr. Math Library:

 Find items containing (put spaces between keywords):   Click only once for faster results: [ Choose "whole words" when searching for a word like age.] all keywords, in any order at least one, that exact phrase parts of words whole words

Submit your own question to Dr. Math
Math Forum Home || Math Library || Quick Reference || Math Forum Search