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已知实数a满足a^2-a-1=0则a^8+7a^-4的值为多少 求的值
人气:123 ℃ 时间:2020-10-01 05:58:41
解答
a^8=[a^2]^4=(a+1)^4=(a^2+2a+1)^2=(a+1+2a+1)^2=(3a+2)^2=9a^2+12a+4=21a+13 a^4=[a^2]^2=(a+1)^2=3a+2 7a^-4=7/(3a+2) a^8+7a^-4=21a+13+7/(3a+2)
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