Tìm số nguyên a biết: |a + 7| = 2

- Hướng dẫn giải

$$\begin{gathered} \left|\mathrm{a}+7\right|=2 \\ \Rightarrow \mathrm{a}+7=2 \mathrm{hoặc} \mathrm{a}+7=-2 \\ \begin{array}{l}\ast \text{TH1}:\mathrm{a}+7=2\\ \mathrm{a}=2-7\\ \mathrm{a}=-5.\end{array} \\ \begin{array}{l}\ast \text{TH2:\hspace{0.17em}\hspace{0.17em}}\mathrm{a}+7=-2\\ \mathrm{a}=-2-7\\ \mathrm{a}=-9.\end{array} \\ \mathrm{Vậy} \mathrm{a} = -5 \mathrm{hoặc} \mathrm{a} = -9 \end{gathered}$$