1.(1/x＾3-1/x＾2)×x＾3/x-1
=(1-x)/x^3*x^3/(x-1)
=-1
2.x/2-x-4-x＾2/x＾2-4x+4
=x/(2-x)-(2-x)(2+x)/(x-2)^2
=x/(2-x)+(2+x)/(x-2)
=(-x+2+x)/(x-2)
=2/(x-2)
3.x/(x+1)-(x＾2+1)/(x＾2+x)
=x/(x+1)-(x^2+1)/x(x+1)
=(x^2-x^2-1)/x(x+1)
=-1/x(x+1)
4.2/a＾2-1+1/a+1
=2/(a+1)(a-1)+1/(a+1)
=(2+a-1)/(a+1)(a-1)
=(a+1)/(a+1)(a-1)
=1/(a-1)