Cộng, trừ các phân thức sau: x^2 +2 /x^3 -1 + 2/x^2 +x +1 +1/1-x

* Hướng dẫn giải

$\begin{array}{l}\frac{{\mathrm{x}}^2+2}{{\mathrm{x}}^3-1}+\frac{2}{{\mathrm{x}}^2+\mathrm{x}+1}+\frac{1}{1-\mathrm{x}}=\frac{{\mathrm{x}}^2+2+2\mathrm{x}-2-{\mathrm{x}}^2-\mathrm{x}-1}{\left(\mathrm{x}-1\right)\left({\mathrm{x}}^2+\mathrm{x}+1\right)}\\ =\frac{\mathrm{x}-1}{\left(\mathrm{x}-1\right)\left({\mathrm{x}}^2+\mathrm{x}+1\right)}=\frac{1}{{\mathrm{x}}^2+\mathrm{x}+1}\end{array}$