ace4587
幼苗
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原式=[1/(a+1)]-[(a+3)/(a²-1)]×[(a²-2a+1)/(a²+4a+3)]
=[1/(a+1)]-{(a+3)/[(a+1)(a-1)]}×{(a-1)²/[(a+1)(a+3)]}
=[1/(a+1)]-[(a-1)/(a+1)²]
=[(a+1)/(a+1)²]-[(a-1)/(a+1)²]
=[(a+1)-(a-1)]/(a+1)²
=2/(a+1)²
∵ a²+2a-1=0
∴ a²+2a+1=2
∴ (a+1)²=2
∴ 原式=2/2=1
1年前
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