factorise x4 +x2 +1
Let x2= p
Then x4= p2
x4+ x2+ 1
= p2+ p + 1
= p2+ 1 + p
= (p)2+ (1)2+ 2*p*1 - p
= (p)2+ (1)2+ 2p - p
= (p + 1)2- p
= (p + 1)2- (√p)2
= (p + 1 + √p) (p + 1 - √p)
Substituting the value of p,
( x2+ 1 + √x2) (x2+ 1 - √x2)
= (x2+ 1 +x) (x2+ 1 - x)