Since $\frac{\left(x^{2}+1\right)^{2}}{x^{2}}$ and $\frac{\left(x^{2}-1\right)^{2}}{x^{2}}$ have the same denominator, add them by adding their numerators.
Since $\frac{\left(x^{2}+1\right)^{2}}{x^{2}}$ and $\frac{\left(x^{2}-1\right)^{2}}{x^{2}}$ have the same denominator, add them by adding their numerators.