SOLUTION: 27) The numbers for which the rational expression is undefined are {{{(r^3-7r)/(r^2-49)}}}

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Question 132142: 27) The numbers for which the rational expression is undefined are %28r%5E3-7r%29%2F%28r%5E2-49%29
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

%28r%5E3-7r%29%2F%28r%5E2-49%29 Start with the given expression


r%5E2-49=0 Set the denominator equal to zero. Remember, dividing by 0 is undefined. So if we find values of r that make the denominator zero, then we must exclude them from the domain.




%28r-7%29%28r%2B7%29=0 Factor the left side (note: if you need help with factoring, check out this solver)




Now set each factor equal to zero:

r-7=0 or r%2B7=0

r=7 or r=-7 Now solve for r in each case


So our solutions are r=7 or r=-7



Since r=-7 and r=7 make the denominator equal to zero, this means r=-7 and r=7 make the rational expression undefined (remember you cannot divide by zero)