division by zero is undefined, so you must exclude values where the denominator is zero.
x^2 - 49 = (x-7)(x+7)
so, ...
You have to exclude them before simplifying, because in the original expression, 0/0 is still undefined. Canceling the offending factors makes the fraction simpler, but the original fraction is still undefined where the denominator is zero, even if the numerator is too.
These are 2 questions that I need help with from my math assignment. My teacher isn't much help, she doesn't respond ):
1. (2x-31)/(x^2-49) . Identify any nonpermissible values.
2.Using an example, explain why non-permissible values must be noted before simplifying rational expressions and equations
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