Cho biểu thức P = (x^2 + 1/ x+1 -1)(4/x-1 - 2/x)

* Hướng dẫn giải

a) P xác định khi $\mathrm{x}\ne \pm 1,\mathrm{x}\ne 0$

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