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a) 15 . (27 + 18 + 6 ) + 15 . ( 23 +12 ) = 15. 51 + 15 . 35 = 765 + 525 = 1290
b) 14 . 35 . 5 + 10 . 25 . 7 + 20 . 70 = 2450 + 1750 + 1400 = 2452450
c) 53 . ( 51 + 4 ) + 53 . ( 49 + 96 ) + 53 = 53 . 55 + 53 . 145 + 53 = 2915 . 7685 = 22401775
d) 46 . ( 27 +75 ) +8 . ( 58 + 25 ) + 8 . ( 58 + 25 ) . 2 = 46 . 102 + 8 . 83 + 8 . 83 = 4692 + 664 + 664 = 6020
a; \(\dfrac{9}{27}\) + \(\dfrac{7}{-49}\)
= \(\dfrac{1}{3}\) - \(\dfrac{1}{7}\)
= \(\dfrac{7}{21}\) - \(\dfrac{3}{21}\)
= \(\dfrac{4}{21}\)
b; - \(\dfrac{12}{10}\) + \(\dfrac{-25}{30}\)
= - \(\dfrac{6}{5}\) - \(\dfrac{5}{6}\)
= -\(\dfrac{36}{30}\) - \(\dfrac{25}{30}\)
= \(\dfrac{-61}{30}\)
c; \(\dfrac{-20}{35}\) + \(\dfrac{-16}{-24}\)
= - \(\dfrac{4}{7}\) + \(\dfrac{2}{3}\)
= - \(\dfrac{12}{21}\) + \(\dfrac{14}{21}\)
= \(\dfrac{2}{21}\)
d; - \(\dfrac{21}{77}\) + \(\dfrac{10}{-35}\)
= - \(\dfrac{3}{11}\) - \(\dfrac{2}{7}\)
= - \(\dfrac{21}{77}\) - \(\dfrac{22}{77}\)
= - \(\dfrac{43}{77}\)
3:
a: (a-b+c)-(c-b-a)
=a-b+c-c+b+a
=2a
b: \(-\left(a-b\right)+\left(b-c+a\right)-\left(a+b-c\right)\)
\(=-a+b+b-c+a-a-b+c\)
\(=b-a\)
c: \(-\left(a-b-c\right)-\left(-a+b+c\right)-\left(a-b+c\right)\)
\(=-a+b+c+a-b-c-a+b-c\)
\(=-a+b-c\)
2:
a: \(12-\left(-12\right)=12+12=24\)
b: \(-\left(35-49\right)+\left(27-49\right)=-35+49+27-49\)
=-35+27
=-8
c: \(47-\left(59-63\right)+\left(63-47\right)\)
\(=47-59+63+63-47\)
=126-59
=67
d: \(-\left(-20\right)-\left(-30\right)-70\)
=20+30-70
=50-70
=-20
a: \(x-\dfrac{10}{3}=\dfrac{7}{15}\cdot\dfrac{3}{5}\)
=>\(x-\dfrac{10}{3}=\dfrac{21}{75}=\dfrac{7}{25}\)
=>\(x=\dfrac{7}{25}+\dfrac{10}{3}=\dfrac{21+250}{75}=\dfrac{271}{75}\)
b: \(x+\dfrac{3}{22}=\dfrac{27}{121}\cdot\dfrac{9}{11}\)
=>\(x+\dfrac{3}{22}=\dfrac{243}{1331}\)
=>\(x=\dfrac{243}{1331}-\dfrac{3}{22}=\dfrac{123}{2662}\)
c: \(\dfrac{8}{23}\cdot\dfrac{46}{24}-x=\dfrac{1}{3}\)
=>\(\dfrac{8}{24}\cdot\dfrac{46}{23}-x=\dfrac{1}{3}\)
=>\(\dfrac{2}{3}-x=\dfrac{1}{3}\)
=>\(x=\dfrac{2}{3}-\dfrac{1}{3}=\dfrac{1}{3}\)
d: \(1-x=\dfrac{49}{65}\cdot\dfrac{5}{7}\)
=>\(1-x=\dfrac{49}{7}\cdot\dfrac{5}{65}=\dfrac{7}{13}\)
=>\(x=1-\dfrac{7}{13}=\dfrac{6}{13}\)
Bài 1:
a) 248 + (-12) + 2064 + (-236)
= 248 - 236 + 2064 - 12
= 12 + 2052
= 2064
b) (-298) + (-300) + (-302)
= -298 - 302 - 300
= -600 - 300
= -900
c) 5 + (-7) + 9 + (-11) + 13 + (-15)
= -2 - 2 - 2
= -6
d) (-6) + 8 + (-10) + 12 + (-14) + 16
= 2 + 2 + 2
= 6
e) 456 + [58 + (-456) + (-38)]
= 456 - 456 + 58 - 38
= 0 + 20
= 20
Bài 2:
a) 8 - (3 + 7)
= 8 - 3 - 7
= -2
b) (-5) - (9 - 12)
= -5 - 9 + 12
= -2
c) (5674 - 97) + (97 + 18 - 5674)
= 5674 - 97 + 97 + 18 - 5674
= 18
d) (13 - 135 + 49) - (13 + 49)
= 13 - 13 - 135 + 49 - 49
= -135
e) x + 8 - (x + 22)
= x + 8 - x - 22
= -14
f) - (x + 5) + (x + 10) - 5
= -x - 5 + x + 10 - 5
= 0
a) 3x + 27 = 9
=> 3x = 9 - 27
=> 3x = -18
=> x = -18 : 3
=> x = -6
b) 2x + 12 = 3(x - 7)
=> 2x + 12 = 3x - 3 . 7
=> 2x + 12 = 3x - 21
=> 3x - 2x = 21 - 12
=> x = 9
c) 2x . 2 - 1 = 49
=> 2x . 2 = 49 + 1
=> 2x . 2 = 50
=> 2x = 50 : 2
=> 2x = 25
=> x =25 : 2
=> x = 25/2
d) |-9 - x| - 5 = 12
=> |-9 - x| = 12 + 5
=> |-9 - x| = 17
=> \(\orbr{\begin{cases}-9-x=17\\-9-x=-17\end{cases}}\)
=> \(\orbr{\begin{cases}x=-9-17\\x=-9-\left(-17\right)\end{cases}}\)
=> \(\orbr{\begin{cases}x=-26\\x=8\end{cases}}\)
3x + 27 = 9
3x = 9 - 27
3x = - 18
x = - 6
b, 2x + 12 = 3.( x - 7 )
2x + 12 = 3x - 21
2x - 3x = - 21 - 12
- x = - 33
x = 33
c, 2x2 - 1 = 49
=> 2x2 = 49 + 1
=> 2x2 = 50
=> x2 = 50 : 2
=> x2 = 25
=> x = 5 hoặc x = - 5
d, | - 9 - x | - 5 = 12
| - 9 - x | = 12 + 5
| - 9 - x | = 17
=> - 9 - x = 17 hoặc - 9 - x = - 17
=> x = - 26 hoặc x = 8
\(27.332+93.43+57.61+69.57\\ =27.332+93.43+57.\left(61+69\right)\\ =27.332+93.43+57.130\\ =8964+3999+7410=20373\\ 34.75+75.66-65.100\\ =\left(34+66\right).75-65.100\\ =100.75-65.100\\ =100.\left(75-65\right)\\ =100.10=1000\\ \left(456.11+912\right).37:13:74\\ =5928:13:\left(74:37\right)\\ =456:2=228\\ 6^2:4.3+2.5^2\\ =36:4.3+2.25\\ =9.3+50=27+50=77\\ 5.4^2-18:3^2\\ =5.16-18:9\\ =80-2=78\\\left[\left(315+372\right).3+\left(372+315\right).7\right]:\left(26.13+74.14\right)\\ =687.\left(3+7\right):\left(338+1036\right)\\ 687.10:1374\\ =6870:1374=5\\ 12:\left\{390:\left[500-\left(125+35.7\right)\right]\right\}\\ =12:\left[390:\left(500-370\right)\right]\\ =12:\left(390:130\right)=12:3=4\\ 192000-\left(1500.2+1800.3+1800.2:3\right)\\ =192000-\left(3000+5400+1200\right)\\ =192000-9600=182400\)
a, \(\left|-46\right|+\left|12\right|+\left|100\right|=46+12+100=158\)
b, \(27\cdot\left(-2\right)^3\cdot\left(-7\right)\cdot\left(49\right)-456=27\cdot\left(-8\right)\cdot\left(-7\right)\cdot49-456=76033\)
# k dùm
\(\left|-46\right|+\left|+12\right|+\left|+100\right|\)
\(=46+12+100\)
\(=58+100\)
\(=158\)