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Bài 1:
a; \(\dfrac{5}{18}\) + \(\dfrac{8}{19}\) - \(\dfrac{7}{21}\) + (- \(\dfrac{10}{36}\) + \(\dfrac{11}{19}\) + \(\dfrac{1}{3}\)) - \(\dfrac{5}{8}\)
= \(\dfrac{5}{18}\) + \(\dfrac{8}{19}\) - \(\dfrac{1}{3}\) -\(\dfrac{10}{36}\) + \(\dfrac{11}{19}\) + \(\dfrac{1}{3}\) - \(\dfrac{5}{8}\)
= (\(\dfrac{5}{18}\) - \(\dfrac{10}{36}\)) + (\(\dfrac{8}{19}\) + \(\dfrac{11}{19}\)) - (\(\dfrac{1}{3}\) - \(\dfrac{1}{3}\)) - \(\dfrac{5}{8}\)
= (\(\dfrac{5}{18}\) - \(\dfrac{5}{18}\)) + \(\dfrac{19}{19}\) - 0 - \(\dfrac{5}{8}\)
= 0 + 1 - \(\dfrac{5}{8}\)
= \(\dfrac{3}{8}\)
b; \(\dfrac{1}{13}\) + (\(\dfrac{-5}{18}\) - \(\dfrac{1}{13}\) + \(\dfrac{12}{17}\)) - (\(\dfrac{12}{17}\) - \(\dfrac{5}{18}\) + \(\dfrac{7}{5}\))
= \(\dfrac{1}{13}\) - \(\dfrac{5}{18}\) - \(\dfrac{1}{13}\) + \(\dfrac{12}{17}\) - \(\dfrac{12}{17}\) + \(\dfrac{5}{18}\) - \(\dfrac{7}{5}\)
= (\(\dfrac{1}{13}\) - \(\dfrac{1}{13}\)) + (\(\dfrac{12}{17}\) - \(\dfrac{12}{17}\)) + (-\(\dfrac{5}{18}\) + \(\dfrac{5}{18}\)) - \(\dfrac{7}{5}\)
= 0 + 0 + 0 - \(\dfrac{7}{5}\)
= - \(\dfrac{7}{5}\)
Bài 1 c;
\(\dfrac{15}{14}\) - (\(\dfrac{17}{23}\) - \(\dfrac{80}{87}\) + \(\dfrac{5}{4}\)) + (\(\dfrac{17}{23}\) - \(\dfrac{15}{14}\) + \(\dfrac{1}{4}\))
= \(\dfrac{15}{14}\) - \(\dfrac{17}{23}\) + \(\dfrac{80}{87}\) - \(\dfrac{5}{4}\) + \(\dfrac{17}{23}\) - \(\dfrac{15}{14}\) + \(\dfrac{1}{4}\)
= (\(\dfrac{15}{14}-\dfrac{15}{14}\)) + (\(-\dfrac{17}{23}+\dfrac{17}{23}\)) - (\(\dfrac{5}{4}\) - \(\dfrac{1}{4}\)) + \(\dfrac{80}{87}\)
= 0 + 0 - 1 + \(\dfrac{80}{87}\)
= - \(\dfrac{7}{87}\)
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a)5.4 – 18 : 9 b)17. (85 + 15) – 120
= 20 – 2 = 17.100 – 120
= 18 = 170 – 120
= 50
c)23.(17 - 14)
= 23.3
= 8.3
= 24
a) 5 . 2\(^2\) - 18 : 3
⇔ 5 . 4 - 18 : 3
⇔ 20 - 6
⇔ 14
b) 17 . 85 + 15 . 17 - 120
⇔ 17 . ( 85 + 15 ) - 120
⇔ 17 . 100 - 120
⇔ 1700 - 120
⇔ 1580
c) 2\(^3\) . 17 - \(2^3\) . 14
⇔ \(2^3\) . ( 17 - 14 )
\(\Leftrightarrow\) 8 . 3
⇔ 24
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 5.2² - 18 : 3
= 5.4 - 18 : 9
= 20 - 2
= 18
b) 17 . 85 + 15 . 17 - 120
= 17 . (85 + 15) - 120
= 17 . 100 - 120
= 1700 - 120
= 1580
c) 2³ . 17 - 2³ . 14
= 8 . 17 - 8 . 14
= 8 . (17 - 14)
= 8 . 3
= 24
a) 5 . 22 – 18 : 32
= 5.4 – 18 : 9
= 20 – 2
= 18
b) 17 . 85 + 15 . 17 – 120
= 17. (85 + 15) – 120
= 17.100 – 120
= 170 – 120
= 50
c) 23 . 17 – 23 . 14
= 23.(17 - 14)
= 23.3
= 8.3
= 24
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 37 (x-15)=0
x-15 =0
x =15
b) (x-17).23=23
x-17 =1
x =1+17
x =18
c) (x-2) (x-4)=0
Th1: x-2=0
x =0+2
x =2
TH2: x-4=0
x =0+4
x =4
Vậy x=2 hoặc x=4
d) (x+12) . 53=1060
x+12 =1060:53
x+12 =20
x =20-12
x =8
e) 4 . (x-50) = 160
x-50 =160:4
x-50 =40
x =40+50
x =90
f) (17-x) : 6=2
17-x =2 . 6
17-x =12
x =17-12
x =5.
Chúc học tốt!
![](https://rs.olm.vn/images/avt/0.png?1311)
\(1,\frac{2}{3}+\frac{4}{9}+\frac{1}{5}+\frac{2}{15}+\frac{3}{2}-\frac{17}{18}\)
\(< =>\frac{4}{9}+\frac{3}{2}+\left(\frac{2}{3}+\frac{1}{5}+\frac{2}{15}\right)-\frac{17}{18}\)
\(< =>\frac{8}{18}+\frac{27}{18}+\left(\frac{10}{15}+\frac{3}{15}+\frac{2}{15}\right)-\frac{17}{18}\)
\(< =>\frac{35}{18}+1-\frac{17}{18}\)
\(< =>\frac{53}{18}-\frac{17}{18}\)
\(< =>2\)
\(2,\frac{13}{28}\cdot\frac{5}{12}-\frac{5}{28}\cdot\frac{1}{12}\)
\(< =>\left(\frac{13}{28}-\frac{5}{28}\right)\cdot\left(\frac{5}{12}-\frac{1}{12}\right)\)
\(< =>\frac{2}{7}\cdot\frac{1}{3}\)
\(< =>\frac{2}{21}\)
\(3,\frac{19}{4}\cdot\frac{15}{23}-\frac{15}{4}\cdot\frac{7}{23}+\frac{15}{4}\cdot\frac{11}{23}\)
\(< =>\frac{285}{92}-\frac{105}{92}+\frac{165}{92}\)
\(< =>\frac{15}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 2317 - 2316 = 2316(23-1) = 2316.22
2316 - 2315 = 2315( 23-1) = 2315.22
Do........... ( tới đây chắc bn làm đc)
b) 1719 + 1717 = 1717( 172+ 1) = 1717. ( 289+1) = 1717 . 290
2 .1718 = 1717 . (17.2) = 1717. 34
Do..................
ko có quy tac đéo ai tính đc
Bạn ơi có khi nào bạn viết thiêu số ko????
Ko quy tắc ai tính đc.