Factories x4+x2+1 . . .

Questin : Factories x⁴+x²+1

Doubt by Veer

Solution : 
x⁴+x²+1
Adding x² and subtracting x² 
=x⁴+x²+1+x²-x²
=x⁴+x²+x²+1-x²
=x⁴+2x²+1-x²
=[x⁴+2x²+1]-x²
=[(x²)²+2(x²)(1)+(1)²]-x²
=[(x²+1)²-x²] [∵a²+2ab+b²=(a+b)²]
=(x²+1-x)(x²+1+x)
=(x²-x+1)(x²+x+1)