Đáp án đúng: C
Giải chi tiết:a) Ta có:
\(\eqalign{& \left( { - \overline {a5} } \right) + \left( { - 85} \right) = - 150 \cr & - \left( {\overline {a5} + 85} \right) = - 150 \cr & \overline {a5} + 85\,\,\,\,\,\,\,\,\,\, = 150 \cr & \overline {a5} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 150 - 85 \cr & \overline {a5} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 65 \cr & \Rightarrow a = 6. \cr} \)
b) Ta có: \(37 + \left( { - \overline {5b} } \right) = - 20 \Rightarrow \left| { - \overline {5b} } \right| > \left| {37} \right| \Rightarrow \overline {5b} > 37\)
Do đó:
\(\eqalign{& 37 + \left( { - \overline {5b} } \right) = - 20 \cr & - \left( {\overline {5b} - 37} \right) = - 20 \cr & \overline {5b} - 37\,\,\,\,\,\,\,\,\, = 20 \cr & \overline {5b} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 20 + 37 \cr & \overline {5b} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 57 \cr & \Rightarrow b = 7. \cr} \)