a, x10+x9+x8-x9-x8-x7+x7+x6+x5-x6-x5-x4+x5+x4+x3-x3-x2-x+x2+x+1 = x8(x2+x+1)-x7(x2+x+1)+x5(x2+x+1)-x4(x2+x+1)+x3(x2+x+1)-x(x2+x+1)+(x2+x+1) =(x8-x7+x5-x4+x3-x+1)
b,x8+x7+x6-x7-x6-x5+x5+x4+x3-x3-x2-x+x2+x+1 =x6( x2+x+1)-x5(x2+x+1)+x3(x2+x+1)-x(x2+x+1)+(x2+x+1) = (x2+x+1)(x6-x5+x3-x+1)
a)Ta có: x10+x5+1=x10+x7-x7+x6-x6+x5+1
=(x10-x7) - (x6-1) + (x7+x6+x5)
=x7(x3-1) - ((x3)2-1) + (x2+x+1)
=x7(x-1)(x2+x+1) - (x3-1)(x3+1) + x5(x2+x+1)
=x7(x-1)(x2+x+1) - (x-1)(x2+x+1)(x3+1) + x5(x2+x+1)
=(x2+x+1)(x7(x+1)-(x+1)(x3+1)+x5)
=(x2+x+1)(x8-x7+x5-x4+x3-x+1)
c) 2x2(x +1) + 4x(x +1); d) 2 x(y - 1) - 2
