Question 177675
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I presume you mean *[tex \huge \frac {r^3-8r}{r^2-16}].


If this is the case, then the entire rational function would be undefined for any value of the variable that makes the denominator expression equal to zero.


So solve:


*[tex \huge r^2-16 = 0],


which rather conventiently factors:


*[tex \huge (r + 4)(r - 4) = 0],


Which means that


*[tex \huge r = -4]


or


*[tex \huge r = 4]


Hence, the original rational expression is undefined for 4, -4

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