①原题应该是这样吧（a²-b²）/（a²-ab）÷{（a²+ 2ab+b²）}/a
如果那个a没有平方,解起来很麻烦的
如果是这样,这样化简：(a-b)(a+b)/a(a-b)÷(a+b)²/a
=(a+b)/a×a/(a+b)²
=1/(a+b)
把a=√2 - 1,b=1 代入 =1/√2
=√2 /2
②{(x-2)-5/(x+2)}÷(x-3)/(2x+4)
={(x-2)(x+2)/(x+2)-5/(x+2)}÷(x-3)/2(x+2)
=(x²-9)/(x+2)×2(x+2)/(x-3)
=(x+3)(x-3)/(x+2)×2(x+2)/(x-3)
=2(x+3)
把x=√2-3代入 =2√2
③1/(a+1) - (a+1)/(a²-2a+1)÷(a+1)/(a-1)
=1/(a+1) - (a+1)/(a-1)²×(a-1)/(a+1)
=1/(a+1) - 1/(a-1)
=(a-1)/{(a-1)(a+1)}-(a+1)/{(a-1)(a+1)}
=-2/{(a-1)(a+1)}
=-2/(a²-1)
=2/(1-a²)
把a=√2代入 =-2