9) 3(x4+x2+1)−(x2+x+1)2
=3x4+3x2+3−(x4+x2+1+2x3+2x+2x2)
= 3x4+3x2+3−x4−x2−1−2x3−2x−2x2
= 2x4−2x3−2x+2
= 2x3.(x−1)−2.(x−1)
= (x−1)(2x3−2)
= (x−1).2.(x3−1)
= (x−1).2.(x−1)(x2+x+1)
= (x−1)2.2.(x2+x+1)
10) 64x4+y4
= (8x2)2+2.8x2.y2+(y2)2−16x2y2
= (8x2+y2)2−(4xy)2
= (8x2+y2−4xy).(8x2+y2+4xy)