Cho A=-10/3+6/7-2/3--8/7, B= 21/2+2/15-9/2+-17/15. So sánh A và B.

8/10

Cho \({\rm{A}} = \frac{{ - 10}}{3} + \frac{6}{7} - \frac{2}{3} - \frac{{ - 8}}{7};\,\,{\rm{B}} = \frac{{21}}{2} + \frac{2}{{15}} - \frac{9}{2} + \frac{{ - 17}}{{15}}\). So sánh A và B.

A = B.

A < B.

A = – B.

A > B.

Giải thích

Đáp án đúng là: B

\({\rm{A}} = \frac{{ - 10}}{3} + \frac{6}{7} - \frac{2}{3} - \frac{{ - 8}}{7} = \left( {\frac{{ - 10}}{3} - \frac{2}{3}} \right) + \left( {\frac{6}{7} - \frac{{ - 8}}{7}} \right) = \frac{{ - 12}}{3} + \frac{{14}}{7} = - 4 + 2 = - 2\).

\({\rm{B}} = \frac{{21}}{2} + \frac{2}{{15}} - \frac{9}{2} + \frac{{ - 17}}{{15}} = \left( {\frac{{21}}{2} - \frac{9}{2}} \right) + \left( {\frac{2}{{15}} + \frac{{ - 17}}{{15}}} \right) = \frac{{12}}{2} + \frac{{ - 15}}{{15}} = 6 - 1 = 5\).

Vì –2 < 5 nên A < B.