a: -15/90=-1/6=-5/30

120/600=1/5=6/30

-75/150=-1/2=-15/30

b: -54/90=-3/5=-216/360

-180/288=-5/8=-225/360

-60/135=-4/9=-160/360

c: 212121/353535=3/5=42/70

131313/141414=13/14=65/70

e:

e₁:40/-90=-4/9=-140/315

-70/-175=4/7=180/315

128/-1440=4/45=28/315

e₂: 164/144=41/36

-936/-324=26/9=104/36

-860/720=43/36

\(\dfrac{5\cdot6+5\cdot7}{5\cdot8+20}=\dfrac{5\cdot6+5\cdot7}{5\cdot4\cdot2+5\cdot4}=\dfrac{5\cdot\left(6+7\right)}{5\cdot4\cdot\left(2+1\right)}=\dfrac{5\cdot13}{5\cdot4\cdot3}=\dfrac{13}{4\cdot3}=\dfrac{13}{12}\)

\(\dfrac{5.6+5.7}{5.8+20}\)

=\(\dfrac{5.\left(6+7\right)}{5.\left(8+4\right)}\)

=\(\dfrac{5.13}{5.12}\)

=\(\dfrac{13}{12}\)

a/\(\dfrac{15}{12}=\dfrac{15:3}{12:3}=\dfrac{5}{4}\)
\(\dfrac{27}{6}=\dfrac{27:3}{6:3}=\dfrac{9}{2}=\dfrac{9\times2}{2\times2}=\dfrac{18}{4}\)
b/\(\dfrac{10}{28}=\dfrac{10:2}{28:2}=\dfrac{5}{14}\)
\(\dfrac{40}{7}=\dfrac{40\times2}{7\times2}=\dfrac{80}{14}\)
c/\(\dfrac{14}{60}=\dfrac{7}{30}\)
\(\dfrac{4}{15}=\dfrac{4\times2}{15\times2}=\dfrac{8}{30}\)
#kễnh

quy đồng mẫu số đâu bạn

phân số nào ???

???

*Rút gọn :

`(8.5-8.2)/16=(8.(5-2))/(8.2)=(8.3)/(8.2)=3/2`

`(11.4-11)/(2-13)=(11.(4-1))/(-11)=(11.3)/(-1.11)=3/(-1)=-3`

*Quy đồng :

- Ta có : `-3=(-3)/1`

UCLN(2,1)=2

$\to\begin{cases} \dfrac32=\dfrac32\\\dfrac{-3}1=\dfrac{-6}2\end{cases}$

− 51 136 = − 3 8 ; − 60 108 = − 5 9 ; 26 − 156 = − 1 6

− 3 8 = − 27 72 ; − 5 9 = − 40 72 ; − 1 6 = − 12 72

− 165 270 = 11 18 ; − 91 156 = − 7 12 ; − 210 1134 = 5 27

11 18 = 66 108 ; − 7 12 = − 63 108 ; 5 27 = 20 108