A) 4/20 + 16/42 + 6/15 + (-3/5) +2/21+(-10/21)+3/20
= $\frac{1}{5}$ + $\frac{8}{21}$ + $\frac{2}{5}$ - $\frac{3}{5}$ + $\frac{2}{21}$ - $\frac{10}{21}$ + $\frac{3}{20}$
= ( $\frac{1}{5}$+ $\frac{2}{5}$ - $\frac{3}{5}$ ) + ( $\frac{8}{21}$ + $\frac{2}{21}$ - $\frac{10}{21}$ )
+ $\frac{3}{20}$
= 0 + 0 + $\frac{3}{20}$ = $\frac{3}{20}$
B) 42/46+250/186+(-2121/2323)+(-125125/143143)
= $\frac{21}{23}$ + $\frac{125}{93}$ - $\frac{21}{23}$ - $\frac{125}{143}$
= ( $\frac{21}{23}$ - $\frac{21}{23}$ ) + $\frac{125}{93}$
- $\frac{125}{143}$
= 0 +$\frac{6250}{13299}$ = $\frac{6250}{13299}$
#Chúc Bạn Học Tốt Nha!!!
