(1,0 điểm) Thực hiện phép tính: a) 2/7 + 5/7 . ( − 7/25 ) . b) − 2/3 ⋅ √ 49/25 + 6/5 ⋅ 2/9 + ( − 2/3 )^2 .

a) \(\frac{2}{7} + \frac{5}{7}.\left( { - \frac{7}{{25}}} \right).\)

\( = \frac{2}{7} - \frac{1}{5}\)

\( = \frac{{10}}{{35}} - \frac{7}{{35}}\)

\( = \frac{3}{{35}}\).

b) \[ - \frac{2}{3} \cdot \sqrt {\frac{{49}}{{25}}} + \frac{6}{5} \cdot \frac{2}{9} + {\left( {\frac{{ - 2}}{3}} \right)^2}\]

\[ = - \frac{2}{3} \cdot \sqrt {{{\left( {\frac{7}{5}} \right)}^2}} + \frac{2}{5} \cdot \frac{2}{3} + {\left( {\frac{2}{3}} \right)^2}\]

\[ = - \frac{2}{3} \cdot \frac{7}{5} + \frac{2}{5} \cdot \frac{2}{3} + \frac{2}{3} \cdot \frac{2}{3}\]

\[ = \frac{2}{3} \cdot \left( { - \frac{7}{5} + \frac{2}{5} + \frac{2}{3}} \right)\]

\[ = \frac{2}{3} \cdot \left( {\frac{{ - 5}}{5} + \frac{2}{3}} \right)\]\[ = \frac{2}{3} \cdot \left( { - 1 + \frac{2}{3}} \right)\]

\[ = \frac{2}{3} \cdot \frac{{ - 1}}{3} = \frac{{ - 2}}{9}\].