(x3+x2-1)(x3-x2+1)

(x3 +x2-1)(x3-x2+1)=
(x3 +(x2-1)) (x3-(x2-1)) =
((x3)2-(x2-1)2) =
(x6-(x4-2x2+1)) =
x6-x4+2x2-1