(1,0 điểm) Thực hiện phép tính: a) 1/3 . ( − 4/5 ) + 1/3 . ( − 1/5 ) .b) ( − 1/2 )^2 . √ 16/25 + √ 81 . ( − 2/3 )^2 − 1 1/2 . √ 4/9 .
Giải thích
Hướng dẫn giải
a) \(\frac{1}{3}.\left( { - \frac{4}{5}} \right) + \frac{1}{3}.\left( {\frac{{ - 1}}{5}} \right)\) \( = \frac{1}{3}.\left( { - \frac{4}{5} - \frac{1}{5}} \right)\) \( = \frac{1}{3}.\left( { - 1} \right)\) \( = \frac{{ - 1}}{3}\). | b) \({\left( { - \frac{1}{2}} \right)^2}.\sqrt {\frac{{16}}{{25}}} + \sqrt {81} .{\left( { - \frac{2}{3}} \right)^2} - 1\frac{1}{2}.\sqrt {\frac{4}{9}} \) \( = \frac{1}{4}.\sqrt {{{\left( {\frac{4}{5}} \right)}^2}} + \sqrt {{9^2}} .\frac{4}{9} - \frac{3}{2}.\sqrt {{{\left( {\frac{2}{3}} \right)}^2}} \) \( = \frac{1}{4}.\frac{4}{5} + 9.\frac{4}{9} - \frac{3}{2}.\frac{2}{3}\) \( = \frac{1}{5} + 4 - 1\)\( = \frac{1}{5} + 3\)\( = \frac{{16}}{5}\). |