Số \(\dfrac{-3}{14}\) là kết quả của phép tính
\(\dfrac{2}{3}-\dfrac{5}{7}.\)\(\dfrac{1}{14}-\dfrac{1}{7}.\)\(\dfrac{1}{2}-\dfrac{5}{7}.\)\(\dfrac{3}{14}-\dfrac{5}{14}.\)Hướng dẫn giải:Ta có:
+) \(\dfrac{2}{3}-\dfrac{5}{7}=\dfrac{14}{21}-\dfrac{15}{21}=-\dfrac{1}{21}\ne-\dfrac{3}{14}.\)
+) \(\dfrac{1}{14}-\dfrac{1}{7}=\dfrac{1}{14}-\dfrac{2}{14}=-\dfrac{1}{14}\ne-\dfrac{3}{14}.\)
+) \(\dfrac{3}{14}-\dfrac{5}{14}=-\dfrac{2}{14}\ne-\dfrac{3}{14}.\)
+) \(\dfrac{1}{2}-\dfrac{5}{7}=\dfrac{7}{14}-\dfrac{10}{14}=-\dfrac{3}{14}.\)
