(1,0 điểm) Thực hiện phép tính: a) 5/12 + ( − 7/24 ) : 3/8 ;b) 4/5 . 3/7 − − 4/7 : √ 25/16 − | − 1 | .
Giải thích
Hướng dẫn giải
a) \(\frac{5}{{12}} + \left( { - \frac{7}{{24}}} \right):\frac{3}{8}\) \( = \frac{5}{{12}} + \left( { - \frac{7}{{24}}} \right).\frac{8}{3}\) \( = \frac{5}{{12}} - \frac{7}{9}\) \( = \frac{{15}}{{36}} - \frac{{28}}{{36}}\) \( = \frac{{ - 13}}{{36}}\). | b) \(\frac{4}{5}.\frac{3}{7} - \frac{{ - 4}}{7}:\sqrt {\frac{{25}}{{16}}} - \left| { - 1} \right|\) \( = \frac{4}{5}.\frac{3}{7} - \frac{{ - 4}}{7}:\sqrt {{{\left( {\frac{5}{4}} \right)}^2}} - 1\) \( = \frac{4}{5}.\frac{3}{7} - \frac{{ - 4}}{7}:\frac{5}{4} - 1\) \( = \frac{4}{5}.\frac{3}{7} - \frac{{ - 4}}{7}.\frac{4}{5} - 1\) \( = \frac{4}{5}.\left( {\frac{3}{7} - \frac{{ - 4}}{7}} \right) - 1\) \( = \frac{4}{5}.1 - 1\) \( = \frac{4}{5} - 1\)\( = \frac{{ - 1}}{5}.\) |