Rút gọn rồi quy đồng mẫu số các phân số.

a) \(\frac{6}{{36}}\) và \(\frac{7}{{49}}\)

Rút gọn:

\(\frac{6}{{36}}\,\, = \,\,\frac{{6\,\,:\,\,6}}{{36\,\,:\,\,6}}\,\, = \,\,\frac{1}{6}\)

\(\frac{7}{{49}}\,\, = \,\,\frac{{7\,\,:\,\,7}}{{49\,\,:\,\,7}}\,\, = \,\,\frac{1}{7}\)

Quy đồng mẫu số:

\(\frac{1}{6}\,\, = \,\,\frac{{1\,\, \times \,\,7}}{{6\,\, \times \,\,7}}\,\, = \,\,\frac{7}{{42}}\)

\(\frac{1}{7}\,\, = \,\,\frac{{1\,\, \times \,\,6}}{{7\,\, \times \,\,6}}\,\, = \,\,\frac{6}{{42}}\)

b) \(\frac{8}{{16}}\) và \(\frac{4}{{20}}\)

Rút gọn:

\(\frac{8}{{16}}\,\, = \,\,\frac{{8\,\,:\,\,8}}{{16\,\,:\,\,8}}\,\, = \,\,\frac{1}{2}\)

\(\frac{4}{{20}}\,\, = \,\,\frac{{4\,\,:\,\,4}}{{20\,\,:\,\,4}}\,\, = \,\,\frac{1}{5}\)

Quy đồng mẫu số:

\(\frac{1}{2}\,\, = \,\,\frac{{1\,\, \times \,\,5}}{{2\,\, \times \,\,5}}\,\, = \,\,\frac{5}{{10}}\)

\(\frac{1}{5}\,\, = \,\,\frac{{1\,\, \times \,\,2}}{{5\,\, \times \,\,2}}\,\, = \,\,\frac{2}{{10}}\)