The perfect square
Let's highlight the perfect square of the square three-member
$$\left(x^{4} + 2 x^{2}\right) + 1$$
To do this, let's use the formula
$$a x^{4} + b x^{2} + c = a \left(m + x^{2}\right)^{2} + n$$
where
$$m = \frac{b}{2 a}$$
$$n = \frac{4 a c - b^{2}}{4 a}$$
In this case
$$a = 1$$
$$b = 2$$
$$c = 1$$
Then
$$m = 1$$
$$n = 0$$
So,
$$\left(x^{2} + 1\right)^{2}$$
General simplification
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$$x^{4} + 2 x^{2} + 1$$
$$\left(x - i\right) \left(x + i\right)$$
Combining rational expressions
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$$x^{2} \left(x^{2} + 2\right) + 1$$
Rational denominator
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$$x^{4} + 2 x^{2} + 1$$
Assemble expression
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$$x^{4} + 2 x^{2} + 1$$
$$\left(x^{2} + 1\right)^{2}$$