So sánh các số hữu tỉ sau bằng cách nhanh nhất:
a) \({\rm{}}{{ - 1} \over 5} < {1 \over {1000}}\)
b) \({{267} \over { - 268}} > {{ - 1347} \over {1343}}\)
c) \({{ - 13} \over {38}} < {{29} \over { - 88}}\)
d) \({\rm{}}{{ - 18} \over {31}} = {{ - 181818} \over {313131}}\)
\({\rm{a}}.{{ - 1} \over 5} < {0 \over {5}} = 0;{1 \over {1000}} > {0 \over {1000}} = 0\)
Vậy \({{ - 1} \over 5} < {1 \over {1000}}\)
Advertisements (Quảng cáo)
b) \({{267} \over { - 268}} = {{ - 267} \over {268}} > {{ - 268} \over {268}} = - 1;\)
\({{ - 1347} \over {1343}} < {{ - 1343} \over {1343}} = - 1\)
Vậy \({{267} \over { - 268}} > {{ - 1347} \over {1343}}\)
c) \({{ - 13} \over {38}} < {{-13} \over { - 39}} = {{ - 1} \over 3};{{29} \over { - 88}} = {{ - 29} \over {88}} > {{ - 29} \over {87}} = {{ - 1} \over 3}\)
Vậy \({{ - 13} \over {38}} < {{29} \over { - 88}}\)
d) \({\rm{}}{{ - 18} \over {31}} = {{ - 18.10101} \over {31.10101}} = {{ - 181818} \over {313131}}\)
Vậy \({\rm{}}{{ - 18} \over {31}} = {{ - 181818} \over {313131}}\)