[tex]E(x)=( \frac{x+1}{x-3}- \frac{2x^{2} +3x-3}{ x^{2} -9}+ \frac{2x-1}{x+3}):( \frac{2x^{2}-18}{ x^{2} +6x+9} \\ \\ \frac{(x+1)(x+3)-(2 x^{2} +3x-3)+(2x-1)(x-3)}{ x^{2} -9} :( \frac{2(x^{2}-9)}{ x^{2} +3x+3x+9}) \\ \\ \frac{ x^{2} +3x+x+3-2 x^{2} -3x+3+(2 x^{2} -6x-x+3)}{(x-3)(x+3)} :\frac{2(x^{2}-9)}{ (x+3) ^{2}} \\ \\ \frac{ x^{2}-6x+9}{(x-3)(x+3)} \cdot \frac{(x+3)(x+3)}{2(x+3)(x-3)} = \\ \\ \frac{ (x-3)^{2} }{(x-3)} \cdot \frac{1}{2(x-3)} = \\ \\E(x)= \frac{1}{2}
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