You can put this solution on YOUR website! Rational expressions are undefined for values that make its denominator zero. So to answer the question, we must figure out what values make zero. In other "words", we need to solve:
To solve this equation we can factor it or use the Quadratic Formula. This factors fairly easily:
(z-9)(z+4) = 0
From the Zero Product Property we know that one of these factors must be zero. So:
z-9 = 0 or z+4 = 0
Solving these we get:
z = 9 or z = -4
These are the values for z that would make the denominator zero and, therefore, the rational expression undefined.
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