a^2+3a+1=0a不为0a+1/a= -3a^3+1/a^3=(a+1/a)^3-3(a+1/a)=-27+3*3=-18a^4+1/a^4=(a^2+1/a^2)^2-2=[(a+1/a)^2-2]^2-2=[(-3)^2-2]^2-2=47
