Thực hiện phép tính: \(\dfrac{-3}{4}-\dfrac{-5}{6}+\dfrac{1}{2}-\dfrac{1}{8}\) \(\dfrac{11}{24}\) \(\dfrac{5}{12}\) \(\dfrac{1}{2}\) \(\dfrac{13}{24}\) Hướng dẫn giải: \(\dfrac{-3}{4}-\dfrac{-5}{6}+\dfrac{1}{2}-\dfrac{1}{8}\) \(=\dfrac{-3}{4}+\dfrac{5}{6}+\dfrac{1}{2}-\dfrac{1}{8}\) \(=\dfrac{-18}{24}+\dfrac{20}{24}+\dfrac{12}{24}-\dfrac{3}{24}\) \(=\dfrac{\left(-18\right)+20+12-3}{24}=\dfrac{11}{24}\)
Biết \(x-\dfrac{4}{5}=\dfrac{2}{15}-\dfrac{1}{3}\). Tìm giá trị của x. \(x=\dfrac{3}{5}\) \(x=\dfrac{4}{5}\) \(x=\dfrac{11}{15}\) \(x=-\dfrac{1}{5}\) Hướng dẫn giải: \(x-\dfrac{4}{5}=\dfrac{2}{15}-\dfrac{1}{3}\) \(\Leftrightarrow x-\dfrac{4}{5}=\dfrac{2}{15}-\dfrac{5}{15}\) \(\Leftrightarrow x-\dfrac{4}{5}=-\dfrac{3}{15}\) \(\Leftrightarrow x=-\dfrac{3}{15}+\dfrac{4}{5}\) \(\Leftrightarrow x=-\dfrac{1}{5}+\dfrac{4}{5}\) \(\Leftrightarrow x=\dfrac{3}{5}\)
Tìm x biết \(\left(\dfrac{7}{8}+x\right)+\dfrac{17}{20}=\dfrac{1}{4}\). \(x=-\dfrac{59}{40}\) \(x=-\dfrac{11}{8}\) \(x=-\dfrac{3}{2}\) \(x=\dfrac{3}{2}\) Hướng dẫn giải: \(\left(\dfrac{7}{8}+x\right)+\dfrac{17}{20}=\dfrac{1}{4}\) \(\Leftrightarrow\dfrac{7}{8}+x=\dfrac{1}{4}-\dfrac{17}{20}\) \(\Leftrightarrow\dfrac{7}{8}+x=-\dfrac{3}{5}\) \(\Leftrightarrow x=-\dfrac{3}{5}-\dfrac{7}{8}\) \(\Leftrightarrow x=-\dfrac{59}{40}\)
Làm tính nhân \(-\dfrac{12}{35}.\dfrac{15}{45}\) \(-\dfrac{4}{35}\) \(\dfrac{3}{45}\) \(-\dfrac{1}{7}\) \(-\dfrac{5}{7}\)
Lũy thừa \(\left(-\dfrac{3}{4}\right)^2\) bằng phân số nào trong số các phân số dưới đây? \(\dfrac{9}{16}\) \(-\dfrac{9}{16}\) \(-\dfrac{6}{8}\) \(\dfrac{6}{8}\)
Thực hiện phép tính: \(\left(3-\dfrac{1}{2}\right).\left(-\dfrac{3}{8}+\dfrac{1}{4}\right)\) \(\dfrac{5}{16}\) \(\dfrac{1}{2}\) \(\dfrac{3}{8}\) \(\dfrac{7}{16}\) Hướng dẫn giải: \(\left(3-\dfrac{1}{2}\right).\left(-\dfrac{3}{8}+\dfrac{1}{4}\right)\) \(=\left(\dfrac{6}{2}-\dfrac{1}{2}\right).\left(-\dfrac{3}{8}+\dfrac{2}{8}\right)\) \(=\left(-\dfrac{5}{2}\right).\left(-\dfrac{1}{8}\right)\) \(=\dfrac{5}{16}\)
Thực hiện phép tính: \(-\dfrac{7}{8}+\dfrac{2}{5}.\dfrac{1}{8}\) \(-\dfrac{33}{40}\) \(-\dfrac{7}{8}\) \(-\dfrac{17}{20}\) \(-\dfrac{31}{40}\) Hướng dẫn giải: \(-\dfrac{7}{8}+\dfrac{2}{5}.\dfrac{1}{8}\) \(=-\dfrac{7}{8}+\dfrac{2}{40}\) \(=\dfrac{-35}{40}+\dfrac{2}{40}\) \(=-\dfrac{33}{40}\)
\(\dfrac{1}{600}\) là kết quả của phép tính nào trong số các phép tính dưới đây? \(-\dfrac{3}{4}.\dfrac{5}{6}\) \(-\dfrac{18}{19}.2\) \(-\dfrac{3}{4}.\dfrac{11}{14}\) \(\dfrac{1}{24}.\dfrac{1}{25}\)
Thực hiện phép tính: \(\dfrac{1}{2}.\dfrac{1}{3}+\dfrac{1}{3}.\dfrac{1}{4}+.....+\dfrac{1}{9}.\dfrac{1}{10}\) \(\dfrac{2}{5}\) \(\dfrac{3}{5}\) \(\dfrac{4}{5}\) \(\dfrac{6}{5}\) Hướng dẫn giải: \(\dfrac{1}{2}.\dfrac{1}{3}+\dfrac{1}{3}.\dfrac{1}{4}+.....+\dfrac{1}{9}.\dfrac{1}{10}\) \(=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+....+\dfrac{1}{9}-\dfrac{1}{10}\) \(=\dfrac{1}{2}-\dfrac{1}{10}\) \(=\dfrac{5}{10}-\dfrac{1}{10}\) \(=\dfrac{4}{10}=\dfrac{2}{5}\)
