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Bài 1:
a: x+1/2=5/6
nên x=5/6-1/2=1/3
b: x+1/4=3/4
nên x=3/4-1/4=2/4=1/2
c: x+3/10=1/2
nên x=1/2-3/10=5/10-3/10=1/5
d: x+1/4=3/8
nên x=3/8-1/4=3/8-2/8=1/8
![](https://rs.olm.vn/images/avt/0.png?1311)
bài 1:
a)lấy mẫu chung là 12,ta có:4/12+5/12=9/12
câu tiếp bằng 5/9
lấy mẫu chung là 9,ta có:7/9-6/9=1/9
b)MSC:35 kết quả bằng 38/35
MSC:12 kết quả bằng -7/12
MSC:35 kết quả bằng 207/35
c)MSC:24 kết quả bằng 11/12
tương tự bằng 1/6
MSC:24 kết quả bằng 13/24
bài 2
a)x=8/2
b)x=6/7-2/3=4/21
c)x=7/3
bài 1 : chỉ cần quy đồng hai số cùng mẫu là đc
bài 2 : xác định thành phần của x rồi tinh
![](https://rs.olm.vn/images/avt/0.png?1311)
a,Cách 1: (6/11 + 5/11 ) x 3/7 Cách 2 :(6/11 + 5/11) x 3/7
= 1 x 3/7 =6/11 x 3/7 + 5/11 x 3/7
= 3/7 = 18/77 + 15/77
= 3/7
b, Cách 1:3/5 x 7/9 - 3/5 x 2/9 Cách 2 :3/5 x 7/9 - 3/5 x 2/9
= 7/15 - 2/15 = 3/5 x (7/9 - 2/9 )
= 1/3 = 3/5 x 5/9
= 1/3
c, Cách 1:(6/7 - 4/7) : 2/5 Cách 2: ( 6/7- 4/7 ) : 2/5
= 2/7 : 2/5 = 6/7 : 2/5 - 4/7 : 2/5
= 5/7 = 15/7 - 10/7
= 5/7
d,Cách 1:8/15 : 2/11 + 7/15 : 2/11 Cách 2:8/15 : 2/11 +7/15 : 2/11
= 88/30 + 77/30 =(8/15+7/15) :2/11
= 11/2 = 1 : 2/11
= 11/2
Bài 2 cậu tự làm nhé !
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(x+\dfrac{4}{9}=\dfrac{5}{27}\)
\(x=\dfrac{5}{27}-\dfrac{4}{9}\)
\(x=-\dfrac{7}{27}\)
b) \(x-\dfrac{4}{11}=\dfrac{7}{33}\)
\(x=\dfrac{7}{33}+\dfrac{4}{11}\)
\(x=\dfrac{19}{33}\)
c) \(\dfrac{8}{5}-x=\dfrac{1}{3}\times\dfrac{2}{5}\)
\(\dfrac{8}{5}-x=\dfrac{2}{15}\)
\(x=\dfrac{8}{5}-\dfrac{2}{15}\)
\(x=\dfrac{22}{15}\)
d) \(x-\dfrac{3}{4}=\dfrac{1}{2}+\dfrac{2}{6}\)
\(x-\dfrac{3}{4}=\dfrac{5}{6}\)
\(x=\dfrac{5}{6}+\dfrac{3}{4}\)
\(z=\dfrac{19}{12}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{1}{2}+x=\dfrac{5}{6}\)
\(\Rightarrow x=\dfrac{5}{6}-\dfrac{1}{2}=\dfrac{5}{6}-\dfrac{3}{6}=\dfrac{2}{6}=\dfrac{1}{3}\)
b) \(x+\dfrac{1}{4}=\dfrac{3}{4}\)
\(\Rightarrow x=\dfrac{3}{4}-\dfrac{1}{4}=\dfrac{2}{4}=\dfrac{1}{2}\)
c) \(x-\dfrac{1}{5}=\dfrac{3}{10}\)
\(\Rightarrow x=\dfrac{3}{10}+\dfrac{1}{5}=\dfrac{3}{10}+\dfrac{2}{10}=\dfrac{5}{10}=\dfrac{1}{2}\)
d) \(\dfrac{5}{6}-x=\dfrac{1}{3}\)
\(\Rightarrow x=\dfrac{5}{6}-\dfrac{1}{3}=\dfrac{5}{6}-\dfrac{2}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)
e) \(\dfrac{3}{10}+x=\dfrac{1}{2}\)
\(\Rightarrow x=\dfrac{1}{2}-\dfrac{3}{10}=\dfrac{5}{10}-\dfrac{3}{10}=\dfrac{2}{10}=\dfrac{1}{5}\)
g) \(x+\dfrac{1}{4}=\dfrac{3}{8}\)
\(\Rightarrow x=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{3}{8}-\dfrac{2}{8}=\dfrac{1}{8}\)
a) 12+x=5612+x=56
⇒x=56−12=56−36=26=13⇒x=56−12=56−36=26=13
b) x+14=34x+14=34
⇒x=34−14=24=12⇒x=34−14=24=12
c) x−15=310x−15=310
⇒x=310+15=310+210=510=12⇒x=310+15=310+210=510=12
d) 56−x=1356−x=13
⇒x=56−13=56−26=36=12⇒x=56−13=56−26=36=12
e) 310+x=12310+x=12
⇒x=12−310=510−310=210=15⇒x=12−310=510−310=210=15
g) x+14=38x+14=38
⇒x=38−14=38−28=18⇒x=38−14=38−28=18
Đọc tiếp
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1: Tính
a, 1/2 x 2/3 x 3/4 = 1/4
b, 7/8 x 8/9 x 9/10 = 7/10
c, 5/14 x 7/15 x 28/7 = 2/3
d, 2 x 1/2 x 3 x 1/3 x 4 x 1/4 x 5 x 1/5 = 1
Bài 2: Tính
a, 7/20 - ( 5/8 - 3/5 ) = 7/20 - 1/40 = 14/40 - 1/40 = 13/40
b, 5/6 + ( 5/9 - 1/4 ) = 5/6 + 11/36 = 30/36 + 11/36 = 41/36
c, 9/10 - ( 2/5 + 3/10 ) + 7/20 = 9/10 - 7/10 + 7/20 = 2/10 + 7/20 = 4/20 + 7/20 = 11/20.
Bài 3: Tìm x:
a, 1/2 + x = 5/6
x = 5/6 - 1/2
x = 1/3
b, 5/6 - x = 1/3
x = 5/6 - 1/3
x = 1/2
c, x - 1/mấy vậy bạn
d, 1/3 x x = 1/6
x = 1/6 : 1/3
x = 1/2
![](https://rs.olm.vn/images/avt/0.png?1311)
`a, 3/4 + 1/2 xx 7/2`
`= 3/4 + 7/4`
`=10/4`
`=5/2`
`b, 6/15 - 1/3 : 5/3`
`= 6/15 - 1/3 xx 3/5`
`= 6/15 - 3/15`
`= 3/15`
`=1/5`
`c, x-4/9 = 3/7 : 9/4`
`=> x-4/9= 3/7 xx 4/9`
`=> x-4/9= 12/63`
`=> x-4/9=4/21`
`=> x= 4/21 +4/9`
`=>x= 40/63`
`d, 7/9 xx 3/5 -1/2=1/5`
`->` sao lại bằng có `x` ko vậy ạ?
`a,`
`3/4+1/2 \times 7/2=3/4+7/4=10/4=5/2`
`b,`
`6/15 - 1/3 \div 5/3=6/15-1/5=1/5`
`c,` Tìm x?
`x-4/9=3/7 \div 9/4`
`x-4/9=4/21`
`x=4/21+4/9`
`x=40/63`
`d, 7/9x \times 3/5-1/2=1/5`
`7/9x \times 3/5=1/5+1/2`
`7/9x \times 3/5=7/10`
`7/9x=7/10 \div 3/5`
`7/9x=7/6`
`x=7/6 \div 7/9=3/2`
`(x-1/2)xx5/3=7/4-1/2`
`(x-1/2)xx5/3=5/4`
`x-1/2=5/4:5/3`
`x-1/2=5/4xx3/5`
`x-1/2=3/4`
`x=3/4+1/2`
`x=5/4`
______________________
`6/x + 1/2=2`
`6/x = 2-1/2`
`6/x= 3/4`
`=> x = 6 : 3/4`
`=> x= 6 xx 4/3`
`=> x= 8`
\(a)(x-\dfrac{1}{2}) \times \dfrac{5}{3}=\dfrac{7}{4}-\dfrac{1}{2}\)
\((x-\dfrac{1}{2})\times \dfrac{5}{3}=\dfrac{7}{4}-\dfrac{2}{4}=\dfrac{5}{4}\)
\(x-\dfrac{1}{2}=\dfrac{5}{4}:\dfrac{5}{3}=\dfrac{3}{4}\)
\(x=\dfrac{3}{4}+\dfrac{1}{2}\)
\(x=\dfrac{3}{4}+\dfrac{2}{4}=\dfrac{5}{4}\)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\(b)\dfrac{6}{x}+\dfrac{1}{2}=2\)
\(\dfrac{6}{x}=2-\dfrac{1}{2}\)
\(\dfrac{6}{x}=\dfrac{4}{2}-\dfrac{1}{2}=\dfrac{3}{2}\)
\(\dfrac{6}{x}=\dfrc{6}{4}\)
\(x=4\)