Rút gọn các biểu thức sau: b) x^3+1/ 1-x^3+ x/ x-1- x+1/ x^2+x++1 ;

b, x3+11−x3+xx−1−x+1x2+x+1=x3+1(1−x)(x2+x+1)−x1−x−x+1x2+x+1

=x3+1−x(x2+x+1)−(1−x)(x+1)(1−x)(x2+x+1)=x3+1−x3−x2−x−1+x2(1−x)(x2+x+1)=−x1−x3=xx3−1