Bài 1:
a, $\frac{1}{8}$ + $\frac{3}{8}$ = $\frac{1}{2}$
b, $\frac{3}{7}$ - $\frac{2}{3}$ = $\frac{3}{7}$ + $\frac{-2}{3}$
= $\frac{9}{21}$ + $\frac{-14}{21}$
= $\frac{-5}{21}$
c, $\frac{4}{13}$ : $\frac{8}{39}$ = $\frac{4}{13}$ × $\frac{39}{8}$
= $\frac{4×39}{13×8}$
= $\frac{1×3}{1×2}$
= $\frac{3}{2}$
d, $\frac{9}{16}$ × $\frac{32}{33}$ = $\frac{9×32}{16×33}$
= $\frac{9×32}{16×33}$
= $\frac{3×2}{1×11}$
= $\frac{6}{11}$
Bài 2:
a, $\frac{2}{3}$ + $\frac{4}{3}$ = 2
b, $\frac{2}{9}$ - $\frac{2}{3}$ = $\frac{2}{9}$ + $\frac{-2}{3}$
= $\frac{2}{9}$ + $\frac{-6}{9}$
= $\frac{-4}{9}$
c, $\frac{6}{17}$ : $\frac{9}{34}$ = $\frac{6}{17}$ × $\frac{34}{9}$
= $\frac{6×34}{17×9}$
= $\frac{2×2}{1×3}$
= $\frac{4}{3}$
d, $\frac{-4}{7}$ × $\frac{7}{-16}$ = $\frac{-4×7}{7×-16}$
= $\frac{1×1}{1×4}$
= $\frac{1}{4}$.
Chúc bạn học tốt !!! Study well !!!
#_Kaiz_
