(1,0 điểm) Thực hiện phép tính: a) ( − 1 4 ) .6 2 11 + 3 9 11 . ( − 1 4 ) ;b) 4. ( − 1 2 ) 3 − 2. √ 1 64 + 3. ∣ ∣ − 1 8 ∣ ∣ .
Hướng dẫn giải
a) \(\left( { - \frac{1}{4}} \right).6\frac{2}{{11}} + 3\frac{9}{{11}}.\left( { - \frac{1}{4}} \right)\) \( = \left( { - \frac{1}{4}} \right).\left( {6\frac{2}{{11}} + 3\frac{9}{{11}}} \right)\) \( = \left( { - \frac{1}{4}} \right).\left( {6 + \frac{2}{{11}} + 3 + \frac{9}{{11}}} \right)\) \( = \left( { - \frac{1}{4}} \right).\left( {9 + \frac{2}{{11}} + \frac{9}{{11}}} \right)\) \( = \left( { - \frac{1}{4}} \right).\left( {9 + 1} \right)\) \( = \left( { - \frac{1}{4}} \right).10\) \( = - \frac{{10}}{4}\) \( = - \frac{5}{2}.\) | b) \(4.{\left( { - \frac{1}{2}} \right)^3} - 2.\sqrt {\frac{1}{{64}}} + 3.\left| {\frac{{ - 1}}{8}} \right|\) \( = 4.\left( { - \frac{1}{8}} \right) - 2.\sqrt {{{\left( {\frac{1}{8}} \right)}^2}} + 3.\left| {\frac{{ - 1}}{8}} \right|\) \( = 4.\left( { - \frac{1}{8}} \right) - 2.\frac{1}{8} + 3.\frac{1}{8}\) \( = \left( { - 4 - 2 + 3} \right).\frac{1}{8}\) \( = \left( { - 3} \right).\frac{1}{8}\) \( = \frac{{ - 3}}{8}.\) |