Đề bài

Tính một cách hợp lí a) \(\frac{5}{{11}} - \frac{{10}}{{19}} + 1,5 + \frac{{17}}{{11}} - \frac{9}{{19}}\); b) \(2\frac{3}{5}.\left( { - \frac{2}{3}} \right) - 2\frac{1}{3}.\left( { - \frac{2}{3}} \right) + {\left( {\frac{2}{3}} \right)^2}\).

Lời giải chi tiết

a) \(\frac{5}{{11}} - \frac{{10}}{{19}} + 1,5 + \frac{{17}}{{11}} - \frac{9}{{19}} \) \(= \left( {\frac{5}{{11}} + \frac{{17}}{{11}}} \right) - \left( {\frac{{10}}{{19}} + \frac{9}{{19}}} \right) + 1,5 \) \(= \frac{{22}}{{11}} - \frac{{19}}{{19}} + 1,5 \) \(= 2,5\); b) \(2\frac{3}{5}.\left( { - \frac{2}{3}} \right) - 2\frac{1}{3}.\left( { - \frac{2}{3}} \right) + {\left( {\frac{2}{3}} \right)^2} \) \(=  - \frac{2}{3}.\left( {2\frac{3}{5} - 2\frac{1}{3} - \frac{2}{3}} \right) \) \(=  - \frac{2}{3}.\left( { - \frac{2}{5}} \right) \) \(= \frac{4}{{15}}\).