Question

\(\frac{2}{7}.\frac{9}{11}+\frac{2}{7}.\frac{5}{11}-\frac{3}{7}.\frac{2}{11}=?\)

Answer 1

\(\frac{2}{7}.\frac{9}{11}+\frac{2}{7}.\frac{5}{11}-\frac{3}{7}.\frac{2}{11}=\frac{2}{7}.\left(\frac{9}{11}+\frac{5}{11}\right)-\frac{3}{7}.\frac{2}{11}=\frac{2}{7}.\frac{14}{11}-\frac{3}{7}.\frac{2}{11}=\left(\frac{2}{7}.7\right).\frac{2}{11}-\frac{3}{7}.\frac{2}{11}\)

\(=\frac{11}{7}.\frac{2}{11}-\frac{3}{7}.\frac{2}{11}=\frac{2}{11}.\left(\frac{11}{7}-\frac{3}{7}\right)=\frac{2}{11}.\frac{8}{11}=\frac{16}{121}\)

Answer 2

=16/21 câu này dễ ợt