\(\dfrac{3}{5}.\dfrac{17}{21}+\dfrac{3}{5}.\dfrac{4}{21}=\dfrac{3}{5}\left(\dfrac{17}{21}+\dfrac{4}{21}\right)=\dfrac{3}{5}.1=\dfrac{3}{5}\)
3/5 . 17/21 +3/5 . 4/21
=3/5 . (17/21 + 4/21)
=3/5 . 1
=3/5
\(\dfrac{3}{5}.\dfrac{17}{21}+\dfrac{3}{5}.\dfrac{4}{21}\)
= \(\dfrac{3.17}{5.21}+\dfrac{3.4}{5.21}\)
= \(\dfrac{1.17}{5.7}+\dfrac{1.4}{5.7}\)
= \(\dfrac{17}{35}+\dfrac{4}{35}\)
= \(\dfrac{17+4}{35}\)
= \(\dfrac{21}{35}=\dfrac{3}{5}\)
\(\dfrac{3}{5}\cdot\dfrac{17}{21}+\dfrac{3}{5}\cdot\dfrac{4}{21}\)
\(=\dfrac{3}{5}\cdot\left(\dfrac{17}{21}+\dfrac{4}{21}\right)\)
\(=\dfrac{3}{5}\)
=3/5.(17/21+4/21)
=3/5.1
=3/5
chúc học tốt nha!