$$x^8-34x^4+1=0$$
$$x^8+1=34x^4$$
$$x^4+\frac{1}{x^4}=34$$
$$x^4+\frac{1}{x^4}+2=36$$
$$\left(x^2+\frac{1}{x^2}\right)^2=36$$
$$x^2+\frac{1}{x^2}=6$$
$$x^2+\frac{1}{x^2}-2=4$$
$$\left(x-\frac{1}{x}\right)^2=4$$
$$x-\frac{1}{x}=2$$........(1)
$$\left(x-\frac{1}{x}\right)^3=8$$
$$x^3-\frac{1}{x^3}-3.x.\frac{1}{x}\left(x-\frac{1}{x}\right)=8$$
$$x^3-\frac{1}{x^3}-3\left(2\right)=8$$
$$x^3-\frac{1}{x^3}-6=8$$
$$x^3-\frac{1}{x^3}=14$$
Hence, the correct answer is Option A
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