x^2+3x+1=0,求x^3+1/x^3与x^7+1/x^7的x^2+3x+1=0 x不等于0两边同时除以xx+1/x=-3x^3+1/x^3=(x+1/x)(x^2-1+1/x^2)=3[(x+1/x)^2-3]=3*[(-3)^2-3]=18x^2+1/x^2=7平方x^4+2+1/x^4=49x^4+1/x^4=47x^7+1/x^7=(x^4+1/x^4)(x...