To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $\left(x^{2}\right)^{2}$ and $x^{2}$ is $x^{4}$. Multiply $\frac{4\left(x^{2}+1\right)^{2}}{x^{2}}$ times $\frac{x^{2}}{x^{2}}$.
Since $-\frac{x\left(x^{4}+1\right)^{2}}{x^{4}}$ and $\frac{4\left(x^{2}+1\right)^{2}x^{2}}{x^{4}}$ have the same denominator, subtract them by subtracting their numerators.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $\left(x^{2}\right)^{2}$ and $x^{2}$ is $x^{4}$. Multiply $\frac{4\left(x^{2}+1\right)^{2}}{x^{2}}$ times $\frac{x^{2}}{x^{2}}$.
Since $-\frac{x\left(x^{4}+1\right)^{2}}{x^{4}}$ and $\frac{4\left(x^{2}+1\right)^{2}x^{2}}{x^{4}}$ have the same denominator, subtract them by subtracting their numerators.