中考2012·资阳题a-2/a²-1÷（a-1-2a-1/a+1）,其中a是方程x²-x=6的根的答案

Question

中考2012·资阳题a-2/a²-1÷（a-1-2a-1/a+1）,其中a是方程x²-x=6的根的答案

Answer 1

(a-2)/(a²-1)÷[(a-1)-(2a-1)/(a+1)]=(a-2)/(a+1)(a-1)÷[(a²-1-2a+1)/(a+1)]=(a-2)/(a+1)(a-1)÷[a(a-2)/(a+1)]=(a-2)/(a+1)(a-1)×[(a+1)/a(a-2)]=1/(a²-a)∵a是方程的根,∴a²-a=6∴原式=1/6...