Quy đồng mẫu số các phân số sau:
a) − 2 21 ; 5 − 24
b) − 7 12 ; 11 − 18
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Bài 2:
a: 1/3=20/60
1/5=12/60
1/12=5/60
b: 1/3=16/48
1/12=4/48
1/48=1/48
Bài 2:
a: 1/3=20/60
1/5=12/60
1/12=5/60
b: 1/3=16/48
1/12=4/48
1/48=1/48
Bài 2:
a: 1/3=20/60
1/5=12/60
1/12=5/60
b: 1/3=16/48
1/12=4/48
1/48=1/48
phân tích ra thừa số nguyên tố
`5=5`
`12=2^2 xx3`
`=>` MSC nhỏ nhất là: `5xx12=60`
`2/5=(2xx12)/(5xx12)=24/60`
`5/12=(5xx5)/(12xx5)=25/60`
a: 6/9 và 6/11
6/9=66/99
6/11=54/99
5/9 và 4/7
5/9=35/63
4/7=20/35
11/12 và 9/24
11/12=22/24
9/24=9/24
b: 13/21 và 4/7
13/21=13/21
4/7=12/21
6/15 và 2/5
6/15=2/5 2/5=2/5
a: 12/21=4/7=8/14
4/56=1/14
b: 12/15=4/5=24/30
6/36=1/6=5/30
15/50=3/10=9/30
c: 63/77=9/11=81/99
60/108=5/9=55/99
-18/27=-2/3=-66/99
d: -26/-156=1/6=7/42
49/-14=-7/2=-147/42
32/112=2/7=12/42
`a,MSC:30`
`1/2=(1xx15)/(2xx15)=15/30`
`2/3=(2xx10)/(3xx10)= 20/30`
`3/5=(3xx6)/(5xx6)=18/30`
`b,MSC:12`
`2/3=(2xx4)/(3xx4)=8/12`
`3/4=(3xx3)/(4xx3)=9/12`
`7/12` giữ nguyên
a) \(-\dfrac{5}{14}=-\dfrac{5.3}{14.3}=-\dfrac{15}{42}\)
\(\dfrac{1}{-21}=-\dfrac{1}{21}=-\dfrac{1.2}{21.2}=-\dfrac{2}{42}\)
b) \(\dfrac{17}{60}=\dfrac{17.3}{60.3}=\dfrac{51}{180}\)
\(\dfrac{-5}{18}=\dfrac{-5.10}{18.10}=-\dfrac{50}{180}\)
\(-\dfrac{64}{90}=-\dfrac{64.2}{90.2}=-\dfrac{128}{180}\)
a)-5/14 và 1/-21
-5/14=-5.-21/14.-2=105/-28
a) \(\dfrac{1}{3}=\dfrac{1.8}{3.8}=\dfrac{8}{24}\)
\(\dfrac{3}{4}=\dfrac{3.6}{4.6}=\dfrac{18}{24}\)
\(\dfrac{5}{8}=\dfrac{5.3}{8.3}=\dfrac{15}{24}\)
b) \(\dfrac{2}{3}=\dfrac{2.4}{3.4}=\dfrac{8}{12}\)
\(\dfrac{3}{4}=\dfrac{3.3}{4.3}=\dfrac{9}{12}\)
\(\dfrac{7}{12}=\dfrac{7}{12}\)
c) \(\dfrac{1}{5}=\dfrac{1.6}{5.6}=\dfrac{6}{30}\)
\(\dfrac{1}{6}=\dfrac{1.5}{6.5}=\dfrac{5}{30}\)
\(\dfrac{1}{30}=\dfrac{1}{30}\)
a: 1/54=1/54
5/6=45/54
b: 3/22=3/22
6/11=12/22
c: 1/2=6/12
2/3=8/12
3/4=9/12
\(\dfrac{7\times2}{1\times2}=\dfrac{14}{2},\dfrac{9}{2};\dfrac{81\times3}{7\times3}=\dfrac{243}{21},\dfrac{9}{21}\\ \dfrac{4\times2}{3\times2}=\dfrac{8}{6},\dfrac{16}{6};\dfrac{5\times3}{2\times3}=\dfrac{15}{6},\dfrac{19\times2}{3\times2}=\dfrac{38}{6}\)
a)
− 2 21 ; 5 − 24 M C = 168 − 2 21 = − 2.8. 21.8 = − 16 168 5 − 24 = − 5 24 = − 5.7 24.7 = − 35 168
b)
− 7 12 ; 11 − 18 M C = 36 − 7 12 = − 7.3 12.3 = − 21 36 11 − 18 = − 11 18 = − 11.2 18.2 = − 22 36