已知:a²-3a+1=0,试求(a²-1/a²)(a-1/a)
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已知:a²-3a+1=0,试求(a²-1/a²)(a-1/a)
已知:a²-3a+1=0,试求(a²-1/a²)(a-1/a)
已知:a²-3a+1=0,试求(a²-1/a²)(a-1/a)
a\²+1=3a
两边除以a
a+1/a=3
两边平方
a²+2+1/a²=9
a²+1/a²=7
则(a-1/a)²
=a²-2+1/a²
=5
所以原式=(a+1/a)(a-1/a)*(a-1/a)
=(a+1/a)(a-1/a)²
=3*5
=15