Question

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

Answer 1

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)