Đúng ghi Đ, sai ghi S. a) 9/10 - 4/10 = (9 - 4)/10 = 5/10 = 1/2

Đúng ghi Đ, sai ghi S.

a) \[\frac{9}{{10}} - \frac{4}{{10}} = \frac{{9 - 4}}{{10}} = \frac{5}{{10}} = \frac{1}{2}\]                    Đ

b) \[\frac{7}{9} - \frac{5}{9} = \frac{{7 - 5}}{{9 - 9}} = \frac{2}{0}\]                     S

c) \[\frac{{15}}{{11}} - \frac{1}{{11}} = \frac{{15 - 1}}{{11 + 11}} = \frac{{12}}{{22}} = \frac{6}{{11}}\]             S

d) \[\frac{9}{7} - \frac{1}{7} = \frac{{9 \times 1}}{{7 \times 7}} = \frac{9}{{49}}\]                         S

Giải thích

b) \[\frac{7}{9} - \frac{5}{9} = \frac{{7 - 5}}{9} = \frac{2}{9}\]

c) \[\frac{{15}}{{11}} - \frac{1}{{11}} = \frac{{15 - 1}}{{11}} = \frac{{14}}{{11}}\]

d) \[\frac{9}{7} - \frac{1}{7} = \frac{{9 - 1}}{7} = \frac{8}{7}\]