Rút gọn phận thức: 9- (x+5)^2 / x^2 + 4x+4

* Hướng dẫn giải

$\begin{array}{l}\frac{9-{\left(\mathrm{x}+5\right)}^2}{{\mathrm{x}}^2+4\mathrm{x}+4}=\frac{3^2-{\left(\mathrm{x}+5\right)}^2}{{\left(\mathrm{x}+2\right)}^2}=\frac{\left(3-\mathrm{x}-5\right)\left(3+\mathrm{x}+5\right)}{{\left(\mathrm{x}+2\right)}^2}\\ =\frac{-\left(\mathrm{x}+2\right)\left(\mathrm{x}+8\right)}{{\left(\mathrm{x}+2\right)}^2}=\frac{-\mathrm{x}-8}{\mathrm{x}+2}\end{array}$