ta thấy \(\left(x^2+\frac{1}{x^2}\right)\left(x^2-\frac{1}{x^2}\right)=\left(x^4-\frac{1}{x^4}\right)\)
\(\left(x^2+\frac{1}{x^2}\right)\left(x^2+\frac{1}{x^2}\right)=\left(x^4+\frac{1}{x^4}\right)+2\)
suy ra \(y=\frac{\left(x^4+\frac{1}{x^4}\right)+2}{\left(x^4-\frac{1}{x^4}\right)}\)
<=> \(y=z+\frac{2}{\left(x^4-\frac{1}{x^4}\right)}\)
<=>\(z=\frac{2}{\left(x^4-\frac{1}{x^4}\right)}-y\)