Hiệu của  2 và \(\frac{9}{{17}}\) là:

a) \(\frac{5}{4} - \frac{1}{2}\) = \(\frac{1}{4} + \frac{1}{2}\)

Giải thích

\(\frac{5}{4} - \frac{1}{2} = \frac{5}{4} - \frac{2}{4} = \frac{3}{4}\)

\(\frac{1}{4} + \frac{1}{2} = \frac{1}{4} + \frac{2}{4} = \frac{3}{4}\)

Vì \(\frac{3}{4} = \frac{3}{4}\) nên \(\frac{5}{4} - \frac{1}{2}\) = \(\frac{1}{4} + \frac{1}{2}\)

c) \(\frac{9}{7} + \frac{1}{4}\) < \(\frac{5}{8}\)

Giải thích

\(\frac{9}{7} + \frac{1}{4} = \frac{{36}}{{28}} + \frac{7}{{28}} = \frac{{43}}{{28}} = \frac{{86}}{{56}}\)

\(\frac{5}{8} = \frac{{35}}{{56}}\)

Vì \(\frac{{35}}{{56}} < \frac{{86}}{{56}}\) nên \(\frac{9}{7} + \frac{1}{4}\) < \(\frac{5}{8}\)

a) \(\frac{{1\,\,450}}{{1\,\,000}} - \frac{{700}}{{1\,\,000}} + \frac{{250}}{{1\,\,000}}\)

= \(\frac{{1\,\,450 - 700 + 250}}{{1\,\,000}}\) = \(\frac{{1\,\,000}}{{1\,\,000}}\) = 1

b) \(\frac{{12}}{5} + \frac{7}{{15}} + \frac{4}{{15}}\)

= \(\frac{{36}}{{15}} + \frac{7}{{15}} + \frac{4}{{15}}\) = \(\frac{{36 + 7 + 4}}{{15}} = \frac{{47}}{{15}}\)