Thực hiện phép tính (tính hợp lí nếu có thể): k) ( 1/4 + − 5/13 ) + ( 2/11 + − 8/13 + 3/4 ) .

k) \(\left( {\frac{1}{4} + \frac{{ - 5}}{{13}}} \right) + \left( {\frac{2}{{11}} + \frac{{ - 8}}{{13}} + \frac{3}{4}} \right)\)

\( = \frac{1}{4} + \frac{{ - 5}}{{13}} + \frac{2}{{11}} + \frac{{ - 8}}{{13}} + \frac{3}{4}\)

\( = \left( {\frac{1}{4} + \frac{3}{4}} \right) + \left( {\frac{{ - 5}}{{13}} + \frac{{ - 8}}{{13}}} \right) + \frac{2}{{11}}\)

\( = \frac{4}{4} + \frac{{ - 13}}{{13}} + \frac{2}{{11}}\)

\( = 1 + \left( { - 1} \right) + \frac{2}{{11}}\)\( = \frac{2}{{11}}.\)