[tex]E(x)=( \frac{2}{x-1} - \frac{1}{x+1} ): \frac{(x+3)(x-1)}{x ^{2}-2x+1 } [/tex]
Se,aduce,la,numitor,comun,in,paranteza(x-1)(x+1)
[tex]E(x)= \frac{2x+2-x+1}{(x -1)(x+1) } * \frac{(x-1) ^{2} }{(x+3)(x-1)} [/tex]
[tex]E(x)= \frac{x+3}{(x-1)(x+1)} * \frac{(x-1) ^{2} }{(x+3)(x-1)} = \frac{1}{x+1} [/tex]