2/7.3/4+5/4.2/7-2/7
=3/14+5/14-2/7
=4/7-2/7
=2/7
2\7 x 3\4 + 5\4 x 2\7 - 2\7
= 2\7 x (3\4 + 5\4 - 1)
= 2\7 x 1
= 2\7
Cách 2:
2\7 x 3\4 + 5\4 x 2\7 - 2\7
= 3\14 + 5\4 x 2\7 - 2\7
= 3\14 + 5\14 - 2\7
= 4\7 - 2\7
= 2\7
ta có
\(\frac{2}{7}x\frac{3}{4}+\frac{5}{4}x\frac{2}{7}-\frac{2}{7}=\frac{2}{7}x\left(\frac{3}{4}+\frac{5}{4}\right)-\frac{2}{7}\)
\(=\frac{2}{7}x2-\frac{2}{7}=\frac{2}{7}\)
= 3/14 + 5/14 - 2/7
= 4/7 - 2/7
= 2/7
KQ la 2/7
