Thực hiện các phép tính sau (tính hợp lý nếu có thể) .
a) \(\frac{{ - 3}}{7} + \frac{5}{7}\)
b) \(\frac{2}{3} + \frac{{ - 3}}{5}\)
c) \(\frac{2}{9} - \left( {\frac{1}{{20}} + \frac{2}{9}} \right)\)
d) \(\frac{{11}}{{23}}.\frac{{12}}{{17}} + \frac{{11}}{{23}}.\frac{5}{{17}} + \frac{{12}}{{23}}\)
Dựa vào quy tắc tính với phân số.
a) \(\frac{{ - 3}}{7} + \frac{5}{7} = \frac{2}{7}\)
b) \(\frac{2}{3} + \frac{{ - 3}}{5} = \frac{{10}}{{15}} + \frac{{ - 9}}{{15}} = \frac{1}{{15}}\)
c) \(\frac{2}{9} - \left( {\frac{1}{{20}} + \frac{2}{9}} \right) = \frac{2}{9} - \frac{1}{{20}} - \frac{2}{9} = - \frac{1}{{20}}\)
d) \(\frac{{11}}{{23}}.\frac{{12}}{{17}} + \frac{{11}}{{23}}.\frac{5}{{17}} + \frac{{12}}{{23}}\)\( = \frac{{11}}{{23}}.\left( {\frac{{12}}{{17}} + \frac{5}{{17}}} \right) + \frac{{12}}{{23}}\) \( = \frac{{11}}{{23}} \cdot 1 + \frac{{12}}{{23}}\)\( = \frac{{23}}{{23}}\)\( = 1\)