SOLUTION: Please help. Find all real numbers that are not in the domain of the following function. Then give the domain in set notation. f(x)=2x/x^2+x-72

Question 887134: Please help.
Find all real numbers that are not in the domain of the following function. Then give the domain in set notation. f(x)=2x/x^2+x-72
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
your equation is f(x) = 2x / (x^2 + x - 72)
factor the denominator to get:
f(x) = 2x / ((x+9)*(x-8))
the domain is all real number except x = -9 and x = 8 because either one of those will make the denominator = 0 and that leads to an answer that is undefined.
in set notation, the domain would be described as x is an element of the real number set such that { x element of R | x <> -9, 8 }
R represents the real number set.
here's a tutorial on set notation that might be helpful.
they do a better job of explaining it than i do.
the important point here is that your domain can be all real number except -9 and 8.
http://www.purplemath.com/modules/setnotn.htm

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