(a的平方+1/a的平方-2)/(2a-2a的-1次方)=(a²+1/a²-2)/(2a-2/a)=[(a²*a²+1-2a²)/a²]/[2(a²-1)/a]=[(a²*a²+1-2a²)]/[2a(a²-1)]=[(a²-1)²]/[2a(a
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