Giải sbt toán 6 tập 2: bài tập 91 trang 27

• \(M = {8 \over 3}.{2 \over 5}.{3 \over 8}.10.{{19} \over {92}} \)

\(= \left( {{8 \over 3}.{3 \over 8}} \right).\left( {{2 \over 5}.10} \right).{{19} \over {92}} \)

\(= 1.4.{{19} \over {92}} \)

\(= {{4.19} \over {92}} \)

\(= {{19} \over {23}}\) 

• \(N = {5 \over 7}.{5 \over {11}} + {5 \over 7}.{2 \over {11}} - {5 \over 7}.{{14} \over {11}} \)

\(= {5 \over 7}.\left( {{5 \over {11}} + {2 \over {11}} - {{14} \over {11}}} \right)\)

\(= {5 \over 7}.{{ - 7} \over {11}} = {{ - 5} \over {11}}\) 

• \(Q = \left( {{1 \over {99}} + {{12} \over {999}} - {{123} \over {9999}}} \right).\left( {{1 \over 2} - {1 \over 3} - {1 \over 6}} \right) \)

\(= \left( {{1 \over {99}} + {{12} \over {999}} - {{123} \over {999}}} \right).\left( {{3 \over 6} + {{ - 2} \over 6} + {{ - 1} \over 6}} \right) \)

\(= \left( {{1 \over {99}} + {{12} \over {999}} - {{123} \over {9999}}} \right).0 = 0 \)