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a: =4/5+1/5+2/3+1/3=1+1=2
b: =17/12+7/12+29/7-8/7=3+2=5
c: =3/5+2/5+16/7-1/7-1/7
=1+2=3
d: =2/5+3/5+2/3+1/3+7/4+1/4
=1+1+2
=4
`5/9xx1/4+4/9xx3/12`
`=5/9xx1/4+4/9xx1/4`
`=1/4xx(5/9+4/9)`
`=1/4xx9/9`
`=1/4xx1`
`=1/4`
60x [7/12+4/15]
60x153/180
=9180/180
b 1/2x2/3x3/4x4/5x5/6x6/7x7/8x8/9=40320/4032
a, \(=\dfrac{1+4}{5}+\dfrac{5+1+3}{9}=1+1=2\)
b, \(=\dfrac{1+4+2}{3}+\dfrac{1+2+5}{6}=\dfrac{6}{3}+\dfrac{8}{6}=2+\dfrac{4}{3}=\dfrac{6+4}{3}=\dfrac{10}{3}\)
1.
=2/5 x 12/3 + 2/5 x 15/3 + 2/5 x 1
= 2/5 x (12/3 + 15/3 + 1)
=2/5 x 1
=2/5
2.a=1;2
a: =20/90+15/90+54/90=89/90
b: =(9/13+4/13)+2/3=1+2/3=5/3
\(=\dfrac{3}{7}\left(\dfrac{5}{4}-\dfrac{2}{9}\right)=\dfrac{3}{7}\cdot\dfrac{45-8}{36}=\dfrac{3}{36}\cdot\dfrac{37}{7}=\dfrac{37}{84}\)
\(\dfrac{3}{7}:\dfrac{4}{5}-\dfrac{3}{7}:\dfrac{9}{2}\)
\(=\dfrac{3}{7}\times\dfrac{5}{4}-\dfrac{3}{7}\times\dfrac{2}{9}\)
\(=\dfrac{3}{7}\times\left(\dfrac{5}{4}-\dfrac{2}{9}\right)\)
\(=\dfrac{3}{7}\times\left(\dfrac{45}{36}-\dfrac{8}{36}\right)\)
\(=\dfrac{3}{7}\times\dfrac{37}{36}\)
\(=\dfrac{37}{84}\)
#DatNe
các số có mẫu giống nhau thì cộng vào thôi !