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a: =>x=5/6-3/4=10/12-9/12=1/12
b: =>x=12-3/5=57/5
c: =>x=3/5+5/7=21/35+25/35=46/35
d: =>x=7/9:3=7/27
e: =>x=7/8x12/5=84/40=21/10
f: =>x=13:5/3=39/5
![](https://rs.olm.vn/images/avt/0.png?1311)
( x + 1) + (x +4) + ...+ ( x + 34) = 222
x*12 + [(1+34) * 12 : 2] = 222
x*12 + 210 = 222
x*12 = 12
x = 1
(x+1)+(x+ 4)+...+(x+34)=222
x*12+(1+4+7...+34)=222
x*12+210=222
x*12=222-210
x*12=12
x=12:12
x=1
các bạn nhớ k cho mình nhé
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a) 8,76 x 34 + 67 x 8,76 - 8,76
= 8,76 x 34 + 67 x 8,76 - 8,76 x 1
= 8,76 x ( 34 + 67 - 1 )
= 8,76 x 100
= 876
b) 12,5 x 3,27 + 67,3 x 12,5
= 12,5 x ( 3,27 + 67,3 )
= 12,5 x 70,57
= 882,125
c) 56,725 x 53,69 + 56,725 x 55,69 + 56,725
= 56,725 x 53,69 + 56,725 x 55,69 + 56,725 x 1
= 56,725 x ( 53,69 + 55,69 + 1 )
= 56,725 x 110,38
= 6261,13055
a) 8,76.34+67.8,76-8,76
=8,76.34+67.8,76-8,76.1
=8,76(34+67-1)
=8,76.100
=876
b)12,5.32,7+67,3.12,5
=12,5(32,7+67,3)
=12,5.100
=1250
c)56,725.53,69+56,725.55,69+56,725
=56,725.53,69+56,725.55,69+56,725.1
=56,725(53,69+55,69+1)
=56,725.109,39
=6205,14775
![](https://rs.olm.vn/images/avt/0.png?1311)
\(28+\left(81-3.x\right):4=40\)
\(\left(81-3.x\right):4=40-28\)
\(\left(81-3.x\right):4=12\)
\(81-3.x=12.4\)
\(81-3.x=48\)
\(3.x=81-48\)
\(3.x=33\)
\(x=33:3\)
\(x=11\)
28+(81-3.x):4=40
(81-3.x):4=40-28
(81-3.x):4=12
81-3.x=12.4
81-3.x=48
3.x=81-48
3.x=33
x=33:3
x=11
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1,45 x 0,36 + 3,6 x 0,9 - 0,36 x 0,45
= 1,45 x 0,36 + 0,36 x 9 - 0,36 x 0,45
= 0,36 x ( 1,45 + 9 - 0,45)
= 0,36 x { (1,45-0,45) + 9}
= 0,36 x { 1 + 9}
= 0,36 x 10
= 3,6
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3.75 : \(\dfrac{1}{4}\) + 3.75 : 0.5 + 3,75 + \(\dfrac{1}{8}\) + 3,75 x 86
= 3,75 : \(\left(\dfrac{1}{4}+0.5+\dfrac{1}{8}\right)\) + 3,75 x 86
= 3,75 : \(\dfrac{7}{8}\) + 322.5
= 4,3 + 322.5 = 326,8
tích hộ chị nha
![](https://rs.olm.vn/images/avt/0.png?1311)
- \(\frac{3}{5}\)và \(\frac{5}{7}\)
Cách 1: Ta có : \(\frac{3}{5}=\frac{3x7}{5x7}=\frac{21}{35}\)
\(\frac{5}{7}=\frac{5x5}{7x5}=\frac{25}{35}\)
Vì \(21< 25\)\(\Rightarrow\frac{3}{5}< \frac{5}{7}\)
Cách 2: Ta có : \(\frac{3}{5}=1-\frac{2}{5}\)
\(\frac{5}{7}=1-\frac{2}{7}\)
Vì \(\frac{2}{5}>\frac{2}{7}\)\(\Rightarrow1-\frac{2}{5}< 1-\frac{2}{7}\)
hay \(\frac{3}{5}< \frac{5}{7}\)
Mấy phần kia cũng tương tự nhé . //Tại nó dài quá ấy,thông cảm nha//
_Học tốt_
![](https://rs.olm.vn/images/avt/0.png?1311)
a,\(\frac{2}{5}+\frac{3}{4}=\frac{8+15}{20}=\frac{23}{20}\)
\(\frac{7}{12}-\frac{2}{7}+\frac{1}{12}=(\frac{7}{12}+\frac{1}{12})-\frac{2}{7}\)
\(=\frac{2}{3}-\frac{2}{7}=\frac{14-6}{21}=\frac{8}{21}\)
\(\frac{12}{17}-\frac{5}{17}-\frac{4}{17}=\frac{7}{17}-\frac{4}{17}=\frac{3}{17}\)
b,\(675,39+342,14=1017,53\)
\(563,87+403,13-328,35=638,65\)
2/5+3/4=23/20
7/12-2/7+1/12=8/21
12/17-5/17-4/173/17
675,39+342,14=1017,53
563,87+403,13-328,35=638,65
![](https://rs.olm.vn/images/avt/0.png?1311)
Tính thuận tiện :
19,76 x 98,68 - 19,76 x 36,49 + 19,76 x 37,81
= ( 98,68 - 36,49 + 37,81 ) x 19,76
= 100 x 19,76
= 1976.
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