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

* Hướng dẫn giải

$\begin{array}{l}\frac{\mathrm{x}-1}{{\mathrm{x}}^3}-\frac{\mathrm{x}+1}{{\mathrm{x}}^3-{\mathrm{x}}^2}+\frac{3}{{\mathrm{x}}^3-2{\mathrm{x}}^2+\mathrm{x}}=\frac{\mathrm{x}-1}{{\mathrm{x}}^3}-\frac{\mathrm{x}+1}{{\mathrm{x}}^2\left(\mathrm{x}-1\right)}+\frac{3}{\mathrm{x}{\left(\mathrm{x}-1\right)}^2}\\ =\frac{{\mathrm{x}}^3-3{\mathrm{x}}^2+3\mathrm{x}-1-{\mathrm{x}}^3+\mathrm{x}+3{\mathrm{x}}^2}{{\mathrm{x}}^3\left(\mathrm{x}-1\right)}=\frac{4\mathrm{x}-1}{{\mathrm{x}}^3\left(\mathrm{x}-1\right)}\end{array}$