a,\(\dfrac{2}{3}\)-\(\dfrac{5}{7}\).\(\dfrac{14}{25}\)
=\(\dfrac{2}{3}\)-\(\dfrac{2}{5}\)
=\(\dfrac{4}{15}\)
b,\(\dfrac{-2}{5}\).\(\dfrac{5}{8}\)+\(\dfrac{5}{8}\).\(\dfrac{3}{5}\)
=\(\dfrac{5}{8}\).(\(\dfrac{-2}{5}\)+\(\dfrac{3}{5}\))
=\(\dfrac{5}{8}\).\(\dfrac{1}{5}\)
=\(\dfrac{1}{8}\)
Giải:
a) \(\dfrac{2}{3}-\dfrac{5}{7}.\dfrac{14}{25}=\dfrac{2}{3}-\dfrac{2}{5}=\dfrac{4}{15}\)
b) \(\dfrac{-2}{5}.\dfrac{5}{8}+\dfrac{5}{8}.\dfrac{3}{5}\)
\(=\dfrac{5}{8}.\left(\dfrac{-2}{5}+\dfrac{3}{5}\right)\)
\(=\dfrac{5}{8}.\dfrac{1}{5}\)
\(=\dfrac{1}{8}\)
c) \(\left(\dfrac{1}{2}\right)^2-1\dfrac{1}{2}+0,5.\dfrac{12}{5}+5\%\)
\(=\dfrac{1}{4}-\dfrac{3}{2}+\dfrac{1}{2}.\dfrac{12}{5}+\dfrac{1}{20}\)
\(=\dfrac{-5}{4}+\dfrac{6}{5}+\dfrac{1}{20}\)
\(=0\)
Chúc bạn học tốt!
c,\(\left(\dfrac{1}{2}\right)^2\)-1\(\dfrac{1}{2}\)+0,5.\(\dfrac{12}{5}\)+5%
=\(\dfrac{1}{4}\)-\(\dfrac{3}{2}\)+\(\dfrac{1}{2}\).\(\dfrac{12}{5}\)+\(\dfrac{1}{20}\)
=\(\dfrac{1}{4}\)-\(\dfrac{3}{2}\)+\(\dfrac{6}{5}\)+\(\dfrac{1}{20}\)
=\(\dfrac{-5}{4}\)+\(\dfrac{6}{5}\)+\(\dfrac{1}{20}\)
=\(\dfrac{-1}{20}\)+\(\dfrac{1}{20}\)
=0
=
