( x + 1/x ) ( x - 1/x ) ( x^2 + 1x^2 - 1 ) ( x^2 + 1x^2 + 1 ) is equal to?

Answer: Option D

$$\left(x+\frac{1}{x}\right)$$ $$\left(x-\frac{1}{x}\right)$$ $$\left(x^2+\frac{1}{x^2}-1\right)$$  $$\left(x^2+\frac{1}{x^2}+1\right)$$
$$\text{ = }\left(x+\frac{1}{x}\right)$$ $$\left(x^2+\frac{1}{x^2}-1\right)$$  $$\left(x-\frac{1}{x}\right)$$ $$\left(x^2+\frac{1}{x^2}+1\right)$$
$$\begin{array}{rl}& \because \left(\text{A}+\text{B}\right)\left({\text{A}}^2-\text{AB}+{\text{B}}^2\right)={\text{A}}^3+{\text{B}}^3\\ & \because \left(\text{A}-\text{B}\right)\left({\text{A}}^2+\text{AB}+{\text{B}}^2\right)={\text{A}}^3-{\text{B}}^3\\ & =\left(x^3+\frac{1}{x^3}\right)\left(x^3-\frac{1}{x^3}\right)\\ & =\boxed{x^6-\frac{1}{x^6}}\end{array}$$