Question 123085
As I interpret your problem, you were given:
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{{{22n^2/(11n)}}} 
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and you are to find the excluded variables.
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In this problem you could make the mistake of simplifying the problem by dividing the 11 in the
denominator into the 22 of the numerator and then dividing the n in the denominator into
the n-squared of the numerator to reduce the expression to:
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{{{22n^2/(11n) = (22/11)*(n^2/n) = 2*n}}}
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Then it would look as if n could be any real value. But that is not the case. The real problem 
you have here is with the n in the denominator. If the n in the denominator is zero, then
you have a division by zero ... and in algebra a division by zero is not allowed. 
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If you took {{{n^2/n}}} and allowed n to be zero, the problem would become zero divided by zero
and that is not allowed. If you did the division first, you would have {{{n^2/n = n}}} and then
if you let n = 0 it would appear OK. But it is not OK because simplifying it first hid the
fact that a division by zero occurred.
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So, summing it all up ... n cannot be zero in this problem. Other than that, n can be any
real number. 
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Hope this helps you to understand the problem.
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