Cho P = ( 7/20 + 11/15 - 15/12):( 11/20 - 26/45) và Q = 5 - 5/3 + 5/9 - 5/27/8 - 8/3 + 8/9 - 8/27 : 15 - 15/11 + 15/121/16 - 16/11 + 16/121. Chọn kết luận đúng: A. P > Q B. P < Q C. P < -

Trả lời:

\[P = \left( {\frac{7}{{20}} + \frac{{11}}{{15}} - \frac{{15}}{{12}}} \right):\left( {\frac{{11}}{{20}} - \frac{{26}}{{45}}} \right)\]

\[P = \left( {\frac{{21}}{{60}} + \frac{{44}}{{60}} - \frac{{75}}{{60}}} \right):\left( {\frac{{99}}{{180}} - \frac{{104}}{{180}}} \right)\]

\[P = \frac{{ - 10}}{{60}}:\frac{{ - 5}}{{180}} = \frac{{ - 10}}{{60}}.\frac{{180}}{{ - 5}} = 6\]

\[Q = \frac{{5 - \frac{5}{3} + \frac{5}{9} - \frac{5}{{27}}}}{{8 - \frac{8}{3} + \frac{8}{9} - \frac{8}{{27}}}}:\frac{{15 - \frac{{15}}{{11}} + \frac{{15}}{{121}}}}{{16 - \frac{{16}}{{11}} + \frac{{16}}{{121}}}}\]

\[Q = \frac{{5\left( {1 - \frac{5}{3} + \frac{1}{9} - \frac{1}{{27}}} \right)}}{{8\left( {1 - \frac{1}{3} + \frac{1}{9} - \frac{1}{{27}}} \right)}}:\frac{{15\left( {1 - \frac{1}{{11}} + \frac{1}{{121}}} \right)}}{{16\left( {1 - \frac{1}{{11}} + \frac{1}{{121}}} \right)}}\]

\[Q = \frac{5}{8}:\frac{{15}}{{16}} = \frac{5}{8}.\frac{{16}}{{15}} = \frac{2}{3}\]

Vì \[6 > \frac{2}{3}\] nên P > Q

Đáp án cần chọn là: A