2a+1/a²-1×a²-2a+1/a²-a - 1/a+1

2a+1/a²-1×a²-2a+1/a²-a - 1/a+1
2a+1/a²-1×a²-2a+1/a²-a - 1/a+1

2a+1/a²-1×a²-2a+1/a²-a - 1/a+1
2a+1/a²-1×a²-2a+1/a²-a - 1/a+1
=（2a+1）/（a+1）（a-1)×(a-1)²/a(a-1) - 1/(a+1)
=(2a+1)/a(a+1)-1/(a+1)
=(2a+1-a)/a(a+1)
=(a+1)/a(a+1)
=1/a
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