Quy đồng mẫu thức các phân số sau: 2x/(x+2)^3

* Hướng dẫn giải

$\frac{2\mathrm{x}}{{\left(\mathrm{x}+2\right)}^3};\frac{\mathrm{x}-2}{2\mathrm{x}{\left(\mathrm{x}+2\right)}^2}, \mathrm{MTC}: 2\mathrm{x}{\left(\mathrm{x}+2\right)}^3$

Nhân tử phụ:

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

Quy đồng:

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