x=1/x则x=±1（x²-5/x-1+1）乘以x³-1/x²-2x除以（x+3）=(x²-5/x)X(x³-1/x²-2x)÷(x+3)=[(x^3-5)/x]X[(x^5-1-2x^3)/x^2]÷(x+3)=(x^3-5)(x^5-2x^3-1)/[x^3(x+3)]当x=1时=(1-5)(1-2-1)/...