a^2-5a-1=0,则a^2+1/a^2=?

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a^2-5a-1=0,则a^2+1/a^2=?
a^2-5a-1=0,则a^2+1/a^2=?

a^2-5a-1=0,则a^2+1/a^2=?
a²-5a-1=0
→a-1/a=5
→(a-1/a)²=25
a²+1/a²=27.