先化简,再求值.2/a-1+（a^2-4a+4）/（a^2-1）×a+1/a-2其中,a=根号2+1

2/a-1+（a^2-4a+4）/（a^2-1）×a+1/a-2
=2/(a-1) +(a-2)²/(a+1)(a-1) ×(a+1)/(a-2)
=2/(a-1)+(a-2)/(a-1)
=a/(a-1)
当a=0时
原式=0
2.[1-（2/1-x）]÷(x+1)-x(x^2-1)/x^2-2x+1=(1-x-2)/(1-x) ×1/(x+1) -x(x+1)(x-1)/(x-1)²
=1/(x-1)-x(x+1)/(x-1)
=(1-x²-x)/(x-1)
=-(x²+x-1)/(x-1)
=0
再问： ��ǵ�a=���2+1
再答： 2/a-1+��a^2-4a+4��/��a^2-1����a+1/a-2=2/(a-1) +(a-2)²/(a+1)(a-1) ��(a+1)/(a-2)=2/(a-1)+(a-2)/(a-1)=a/(a-1)��a=��2+1ʱԭʽ=(��2+1)/��2 =(2+��2)/2