What is the domain of f(x)=x2+1x2−9f(x) = \frac{x^2 + 1}{x^2 - 9}f(x)=x2−9x2+1?
All real numbers except x=±3x = \pm 3x=±3
All real numbers except x=0x = 0x=0
All real numbers except x=1x = 1x=1
All real numbers