3. $\frac{-5}{9}$ . ($\frac{3}{10}$ - $\frac{2}{5}$)
= $\frac{-5}{9}$ . $\frac{-1}{10}$
= $\frac{5}{90}$
= $\frac{1}{18}$
9. $\frac{1}{5}$ - [$\frac{7}{8}$ - ($\frac{3}{4}$ - $\frac{5}{2}$)]
Cách 1:
= 1/5 – [7/8 – (3/4 – 10/4)]
= 1/5 – [ 7/8 – (-7/4)]
= 1/5 – (7/8 + 7/4)
= 1/5 – 21/8
= 8/40 – 105/40
= -97/40
Cách 2:
= 1/5 – (7/8 – 3/4 + 5/2)
= 1/5 – (7/8 – 6/8 + 20/8)
= 1/5 – 21/8
= -97/40
8. -2/3 – (-2/5) – 7/10
= -2/3 + 2/5 – 7/10
= -20/30 + 12/30 – 21/30
= -8/30 – 21/30
= -29/30
13. –(2/5 – 3/4) – (3/4 + 3/5)
= -2/5 + 3/4 – 3/4 - 3/5
= -2/5 – 3/5
= -5/5 = -1
16. (-5/4) : 2 3/5 + 13/4 : 2 3/5
= -5/4 : 13/5 + 13/4 : 13/5
= -5/4 . 5/13 + 13/4 . 5/13
= 5/13 . ( -5/4 + 13/4)
= 5/13 . 8/4
= 10/13
-HỌC TỐT-
Làm vội:vvv
