The factors of x4+x2=25 are
We have,
= 
Adding and subtracting 9x2 in the equation
=
= 
=
Thus the factors of (x4+x2+25) are 
2
The factors of x4+x2=25 are
We have,
=
Adding and subtracting 9x2 in the equation
=
=
=
Thus the factors of (x4+x2+25) are