Производная. f(x)=(x+1/(x^2+3))

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f(x)'=(x+1)'*(x^2+3)-(x+1)*(x^2+3)'/(x^2+3)^2=x^2+3x-(x+1)*2x/(x^2+3)^2=-x^2+x/(x^2+3)^2=x-x^2/(x^4+6x^2+9);