Question

find all numbers for which the rational expression is undefined. (q^3-6q)/(q^2-16)

Answer 1

It's undefined when the denominator is zero


q^2-16=0


(q+4)(q-4)=0


q+4=0 or q-4=0


q=-4 or q=4


So the expression is undefined when q=-4 or q=4

Answer 2

yep, the denom goes bad when q^2 = 16; so avoid 4 and -4