x4+1-2x2
=x4+2x3+x2-2x3-4x2-2x+x2+2x+1
=x2(x2+2x+1)-2x(x2+2x+1)+1(x2+2x+1)
=(x2-2x+1)(x2+2x+1)
=(x-1)2(x+1)2
x^4 +1 -2x^2
=(x^2)^2 - 2. x^2.1 +1
=(x^2-1)^2
x4 + 1 - 2x2
= x4 + 1 - x2 - x2
= (x4 - x2) - (x2 - 1)
= x2.(x2 - 1) - (x2 - 1)
= (x2 - 1).(x2 - 1)
= (x2 - 1)2
Phan tích x4+1-2x2 thành phần tử
x4+1-2x2 =x4+2x3+x2-2x3-4x2-2x+x2+2x+1
=x2(x2+2x+1)-2x(x2+2x+1)+1(x2+2x+1)
=(x2-2x+1)(x2+2x+1)
=(x-1)2(x+1)2