[tex]E(x)= (3-\frac{1}{x}) : \frac{9 x^{2} -1}{3 x^{2} +x} = \\ = \frac{3x-1}{x}* \frac{3 x^{2} +x}{9 x^{2} -1}= \\ = \frac{3x-1}{x}* \frac{x(3x+1)}{(3x+1)(3x-1)} = \\ = 1. [/tex]
[tex]Observatie:~x \in R-\{- \frac{1}{3};0; \frac{1}{3}\},~dar~cred~ca~asta~se~preciza~in \\ enunt. [/tex]
