Consider $\left(1-x^{2}\right)\left(1+x^{2}\right)$. Multiplication can be transformed into difference of squares using the rule: $\left(a-b\right)\left(a+b\right)=a^{2}-b^{2}$. Square $1$.
$$1-\left(x^{2}\right)^{2}=1-x^{4}$$
To raise a power to another power, multiply the exponents. Multiply $2$ and $2$ to get $4$.
Consider $\left(1-x^{2}\right)\left(1+x^{2}\right)$. Multiplication can be transformed into difference of squares using the rule: $\left(a-b\right)\left(a+b\right)=a^{2}-b^{2}$. Square $1$.
$$1-\left(x^{2}\right)^{2}=1-x^{4}$$
To raise a power to another power, multiply the exponents. Multiply $2$ and $2$ to get $4$.
