已知a+1/a=3,试求aˆ2+1/aˆ2,aˆ4+1/aˆ4的值
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已知a+1/a=3,试求aˆ2+1/aˆ2,aˆ4+1/aˆ4的值
已知a+1/a=3,试求aˆ2+1/aˆ2,aˆ4+1/aˆ4的值
已知a+1/a=3,试求aˆ2+1/aˆ2,aˆ4+1/aˆ4的值
a+1/a=3
则(a+1/a)²=a²+1/a²+2=3²=9
则a²+1/a²=7
两边再平方得a^4+1/a^4+2=49
则a^4+1/a^4=47
a^2+1/a^2=(a+1/a)^2-2=9-2=7
a^4+1/a^4=(a^2+1/a^2)^2-2=49-2=47