Nội dung bài giảng
Tính:
a) \({\rm{}}{{ - 5} \over {13}}.26\) b) \({\left( {{{ - 2} \over 7}} \right)^2}\)
c) \(\left( {2 - {1 \over 2}} \right).\left( {{{ - 3} \over 4} + {1 \over 2}} \right)\)
Giải
a) \({\rm{}}{{ - 5} \over {13}}.26 = {{ - 5.26} \over {13}} = - 10\)
b) \({\left( {{{ - 2} \over 7}} \right)^2} = {{ - 2} \over 7}.{{ - 2} \over 7} = {{\left( { - 2} \right).\left( { - 2} \right)} \over {7.7}} = {4 \over {49}}\)
c) \(\left( {2 - {1 \over 2}} \right).\left( {{{ - 3} \over 4} + {1 \over 2}} \right) \)
\(= \left( {{4 \over 2} - {1 \over 2}} \right).\left( {{{ - 3} \over 4} + {1 \over 2}} \right) \)
\(= {3 \over 2}.{{ - 1} \over 4} = {{3.( - 1)} \over {2.4}} = {{ - 3} \over 8}\)