Expression vs. Equation

Date: 03/20/2003 at 20:02:33
From: Mary Hahn
Subject: It is about expressions and equations

What is the difference between an expression and an equation?

Date: 03/20/2003 at 22:40:18
From: Doctor Peterson
Subject: Re: It is about expressions and equations

Hi, Mary.

An equation is a mathematical "sentence" that says that two things 
are equal; for example

    3x + 1 = 5

says that if you multiply x by 3 and add 1, you will get 5.

An expression is a mathematical "phrase" that stands for a single 
number; for example,

    3x + 1

is an expression whose value is three times the value of x, plus 1, 
whatever value the variable x might have. An expression can also be a 
single number or variable, since those have a numerical value.

An equation consists of two expressions connected by an equals sign. 
It can only be true or false. An expression is never true or false, 
but just has a numerical value.

We might add, by the way, that a variable is a mathematical pronoun, 
which can stand for some value.

If you have any further questions, feel free to write back.

- Doctor Peterson, The Math Forum
  http://mathforum.org/dr.math/