Đâu là giá trị của biểu thức \(A=\left(\dfrac{-5}{17}\right).\dfrac{3}{10}+\dfrac{7}{5}.\left(\dfrac{-5}{17}\right)?\)
\(\dfrac{-1}{2}.\)\(\dfrac{1}{2}\).\(-2.\)\(2.\)Hướng dẫn giải:\(A=\dfrac{-5}{17}.\dfrac{3}{10}+\dfrac{7}{5}.\dfrac{-5}{17}\\ A=\dfrac{-5}{17}.\Big(\dfrac{3}{10}+\dfrac{7}{5}\Big)\\ A=\dfrac{-5}{17}.\Big(\dfrac{3}{10}+\dfrac{14}{10}\Big)\\ A=\dfrac{-5}{17}.\dfrac{17}{10}\\ A=\dfrac{-1}{2}.\)
