已知a^2=a+1;a^8+7a^(-4)=(a+1)^4+7/(a^2+2a+1)= (a^2+2a+1)^2+7/(a^2+2a+1)=9a^2+12a+4+7/(a^2+2a+1)=21a+13+7/(3a+2)=（96+143a）/(3a+2)由a^2=a+1=>a=(1+根号5）/2将a带入上式=>原式=50-根号5 或者=50+根号5不知...