(1,5 điểm) Thực hiện phép tính: a) 13/25 − 11/4 − 28/25 + 15/4 ;b) ( − 1/2 )^2 − 5/8 : ( 0 , 5 )^3 − 5/3 . ( − 6 ) ;c) ( 2/3 − 1/6 )^2 + 1/2 3 . | − 0 , 25 | − 3. √ 1 16 .
Hướng dẫn giải
a) \(\frac{{13}}{{25}} - \frac{{11}}{4} - \frac{{28}}{{25}} + \frac{{15}}{4}\) \( = \left( {\frac{{13}}{{25}} - \frac{{28}}{{25}}} \right) + \left( {\frac{{15}}{4} - \frac{{11}}{4}} \right)\) \( = \frac{{ - 15}}{{25}} + \frac{4}{4}\) \( = \frac{{ - 3}}{5} + 1\) \( = \frac{2}{5}\). | b) \({\left( { - \frac{1}{2}} \right)^2} - \frac{5}{8}:{\left( {0,5} \right)^3} - \frac{5}{3}.\left( { - 6} \right)\) \( = \frac{1}{4} - \frac{5}{8}:0,125 + 10\) \( = \frac{1}{4} - \frac{5}{8}:\frac{1}{8} + 10\) \( = \frac{1}{4} - \frac{5}{8}.8 + 10\) \( = \frac{1}{4} - 5 + 10\) \( = \frac{1}{4} + 5\) \( = \frac{{21}}{4}\). | c) \({\left( {\frac{2}{3} - \frac{1}{6}} \right)^2} + 1\frac{2}{3}.\left| { - 0,25} \right| - 3.\sqrt {\frac{1}{{16}}} \) \( = {\left( {\frac{1}{2}} \right)^2} + \frac{5}{3}.0,25 - 3.\sqrt {{{\left( {\frac{1}{4}} \right)}^2}} \) \( = \frac{1}{4} + \frac{5}{3}.\frac{1}{4} - 3.\frac{1}{4}\) \( = \frac{1}{4} \cdot \left( {1 + \frac{5}{3} - 3} \right)\) \( = \frac{1}{4}.\left( {\frac{5}{3} - 2} \right)\) \( = \frac{1}{4}.\left( { - \frac{1}{3}} \right)\) \( = - \frac{1}{{12}}.\) |