x/(x^2+x+1)=a
x=a(x^2+x+1)
x=a(x^2+1)+ax
a(x^2+1)=x-ax
a(x^2+1)=x(1-a) 平方
a^2(x^2+1)^2=x^2(1-a)^2
a^2(x^4+2x^2+1)=a^2x^2-2ax^2+x^2
a^2(x^4+x^2+1)+a^2x^2=a^2x^2-2ax^2+x^2
a^2(x^4+x^2+1)=x^2(1-2a)
x^2/(x^4+x^2+1)=a^2/(1-2a)
x/(x^2+x+1)=a
x=a(x^2+x+1)
x=a(x^2+1)+ax
a(x^2+1)=x-ax
a(x^2+1)=x(1-a) 平方
a^2(x^2+1)^2=x^2(1-a)^2
a^2(x^4+2x^2+1)=a^2x^2-2ax^2+x^2
a^2(x^4+x^2+1)+a^2x^2=a^2x^2-2ax^2+x^2
a^2(x^4+x^2+1)=x^2(1-2a)
x^2/(x^4+x^2+1)=a^2/(1-2a)