Simplifying an Expression
Date: 05/04/99 at 21:31:10 From: (anonymous) Subject: Using a reciprocal to solve an equation I have a problem that is very hard for me: 9x - 3x + 7 - 4x + y - 3 Iahamed@aol.com
Date: 05/05/99 at 11:56:20 From: Doctor Rick Subject: Re: Using a reciprocal to solve an equation Hi, This time you're not asking about equations. This is an expression (it has no equals sign), and I presume you are supposed to simplify it. 9x - 3x + 7 - 4x + y - 3 What you want to do is to reduce the number of operations as much as possible, and to reduce the number of times each variable appears as much as possible. The first thing you can do is to use the commutativity of addition to move the terms around. I will move all the terms containing x to the left, followed by all the terms containing y, then all the numbers without a variable. 9x - 3x - 4x + y + 7 - 3 Now you can add the numbers at the right: 7 - 3 = 4. Let's also combine the terms containing x, using the distributive property: (9 - 3 - 4)x + y + 4 Add the numbers in the parentheses: 2x + y + 4 That's as much as we can do. We have one term with each variable and one with neither, and there is nothing we can do to combine these. If you have trouble with subtraction, you can rewrite a subtraction as addition of a negative number: 9x - 3x = 9x + (-3x) This way you won't get confused when you commute terms. - Doctor Rick, The Math Forum http://mathforum.org/dr.math/
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