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Topic:  Is "variable" confusing to students? 
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Subject:  Is "variable" confusing to students? 
Author:  Susan 
Date:  May 8 2009 
3x + 5
11 = 3x + 5
y = 3x + 5
The first is an algebraic expression containing the "variable" x. In this case,
the variable x can take on any value. It “varies”.
The second is an equation of one variable. We call x a variable but truly it
doesn't vary. It is just an "unknown". We can solve for x and determine it
must equal 2.
In the final case, we have two variables and they do 'vary' depending on each
other’s values.
Should we call the x in the second case an “unknown” and not a variable? I’ve
seen books say, “solve for the unknown”.
I think we confuse students by calling x “variables” in all of these cases when
in case 2, the x does not vary at all.
 
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