x-x分之1=3
x^2-2+1/x^2=9
x^2+1/x^2=11
x^4+1=11x^2
x^4=11x^2-1
x-x分之1=3
x^2-1=3x
x^2=3x+1
x的四次方-2x的三次方-2x的二次方-7x+1分之x的三次方-x的三次方分之1+2
=(x^3-1/x^3 +2)/(x^4-2x^3-2x^2-7x+1)
=((x-1/x)(x^2+1+1/x^2) +2)/(11x^2-1-2x^3-2x^2-7x+1)
=(3*(11+1) +2)/(9x^2-2x^3+2x-9x)
=38/(9x^2-2x^2(x-1/x)-9x)
=38/(9x^2-2x^2*3-9x)
=38/(3*(3x+1)-9x)
=38/(9x+3-9x)
=38/3请问分子为什么会化成38？x^3-1/x^3=(x-1/x)(x^2+1+1/x^2) x-x分之1=3x^2-2+1/x^2=9x^2+1/x^2=11