`-5/13 + 2/5 + (-8)/13 + 3/5-3/7`
`= (-5/13 + (-8)/13)+(2/5 + + 3/5) -3/7`
`= -13/13+ 5/5-3/7`
`=-1+1-3/7`
`=-3/7`
__
`-5/12 . 2/11 + (-5)/12 . 9/11 +5/12`
`= -5/12 . (2/11+9/11)+5/12`
`=-5/12 . 1 +5/12`
`= -5/12 +5/12`
`=0`
`@ ` \(\text{Mạc Nhược Hàn}\)
a/\(-\dfrac{5}{13}+\dfrac{2}{5}+-\dfrac{8}{13}+\dfrac{3}{5}-\dfrac{3}{7}\)
\(=\left(-\dfrac{5}{13}+-\dfrac{8}{13}\right)+\left(\dfrac{2}{5}+\dfrac{3}{5}\right)-\dfrac{3}{7}\)
\(=-1+1-\dfrac{3}{7}\)
\(=0-\dfrac{3}{7}\)
\(=-\dfrac{3}{7}\)
b/\(-\dfrac{5}{12}\cdot\dfrac{2}{11}+-\dfrac{5}{12}\cdot\dfrac{9}{11}+\dfrac{5}{12}\)
\(=\dfrac{5}{12}\cdot\left(-\dfrac{2}{11}\right)+\dfrac{5}{12}\cdot\left(-\dfrac{9}{11}\right)+\dfrac{5}{12}\)
\(=\dfrac{5}{12}\left(-\dfrac{2}{11}+-\dfrac{9}{11}+1\right)\)
\(=\dfrac{5}{12}\cdot0\)
\(=0\)
