$x^{4}+2x^{2}-3=(x^{4}+2x^{2}+1)-2^{2}$ =$(x^{2}+1)^{2}-2^{2}$ =$(x^{2}+1-2)(x^{2}+1+2)$ =$(x^{2}-1)(x^{2}+3)$ =$(x-1)(x+1)(x^{2}+3)$
$x^{4}+2x^{2}-3=(x^{4}+2x^{2}+1)-2^{2}$ =$(x^{2}-1)^{2}-2^{2}$ =$(x^{2}-1-2)(x^{2}-1+2)$ =$(x^{2}-3)(x^{2}+1)$
$x^{4}+2x^{2}-3=(x^{4}+2x^{2}+1)-2^{2}$ =$(x^{2}
+1)^{2}-2^{2}$ =$(x^{2}
+1-2)(x^{2}
+1+2)$ =$(x^{2}-
1)(x^{2}+
3)$ =$(x-1
)(x+1)(x^{2}+3)$