45 - 5 . (12 + 9)

= 45 - 5 . 21

= 45 - 105

= -60

-48 + 48 . (-78) + 48 . (-21)

= -48 + (-48) . 78 + (-48) . 21

= -48 . (78 + 21 + 1)

= -48 . 100

= -4800

45 - 5 . (12 + 9)

= 45 - 5.21

=9 . 5 + 5 .21

= (9 + 21).5

= 30.5

= 150

-48 + 48 .(-78) + 48.(-21)

= 48.(-1 -78 - 21)

= 48.(-100) 

= -4800

k mik nha bn

45-5.(12+9)

=45-5.9+5.12

=45-45+60

=0+60=60

-48+48.(-78)+48.(-21)

= -48+(-48).78+(-48).21

= -48.(78+21+1)

= -48 . 100

= -4800

1)  35.18−5.7.28=−350

2)  45−5(12+9)=−60

1) 35.18-5.7.28

=630-5.7.28

= 630-980

=630+(-980)

=-(980-630)

=-350

1) 35 . 18 - 5 . 7 . 28
= 630 - 35 . 28
= 630 - 980
= -350

2) 45 - 5.(12+9)

= 45-5×21

= 45-105

=-60

3) 31. (-18) + 31. ( - 81) – 31

=31.(-18)+31+81+(-31)

=31.(-18)+[31+ -(31)]+81

câu 5 sai nha

1)  

2)  

1) 35.18-5.7.28

=630-5.7.28

= 630-980

=630+(-980)

=-(980-630)

=-350

a, $-28\cdot41+100\cdot141+41\cdot(-72)$

$=41\cdot[(-28)+(-72)]+100\cdot141$

$=41\cdot(-100)+(-100)\cdot(-141)$

$=(-100)\cdot[41+(-141)]$

$=(-100)\cdot(-100)$

$=100\cdot100$

$=10000$

b, $35\cdot(65-6)-65\cdot(35+6)$

$=35\cdot65+35\cdot(-6)-65\cdot35-65\cdot6$

$=(35\cdot65-65\cdot35)+[35\cdot(-6)+65\cdot(-6)]$

$=0+(-6)\cdot(35+65)$

$=-6\cdot100$

$=-600$

c, $-48+48\cdot(-78)-21\cdot48$

$=-48\cdot1+(-48)\cdot78+(-48)\cdot21$

$=-48\cdot(1+78+21)$

$=-48\cdot(79+21)$

$=-48\cdot100$

$=-4800$

a) -48 + (-35 + 19) - (32 + 45 + 21)

= -48 - 35 + 19 - 32 - 45 - 21

= (-48 - 32) - (35 + 45) + (19 - 21)

= -80 - 80 - 2

= -162

b) -47 + (38 - 13) - (-52 + 31 - 91)

= -47 + 38 - 13 + 52 - 31 + 91

= (-47 - 13) + (38 + 52) - 31

= -60 + 90 - 31

= 30 - 31 = -1

c) 54 + (-37) - (+70) + (-163) - (-246) + (-230

= 54 - 37 - 70 - 163 + 246 - 230

= (54 + 246) - (37 + 163) - (70 + 230)

= 300 - 200 - 300

= -200

còn lại tự lm

Tính hợp lý :

A, (-48)+(-35+19)-(32+45+21)

B, (-47)+(38-13)-(-52+31-91)

C, 54+(-37)-(+70)+(-163)-(-246)+(-230

chócfghv

\(x\) + (-31) - (42) = -45

\(x\) - (31 + 42) = -45

\(x\) - 73 = -45

\(x\)       = -45 + 73

\(x\)      = 28

305 - \(x\) + 14  = 48 + (\(x\) - 23)

(305  + 14) - \(x\) = (48 - 23) + \(x\)

319 - \(x\)           = 25 + \(x\) 

\(x\) + \(x\)              = 319 - 25

2\(x\)                  = 294

   \(x\)                 = 294 : 2

   \(x\)                 = 147

\(x-43=\left(35-x\right)\) - 48

\(x\) - 43 = 35 - \(x\) - 48

\(x\) - 43 = - (48 - 35) - \(x\)

\(x\) - 43  = - 13 - \(x\)

\(x\) + \(x\)    = -13 + 43

2\(x\)         = 30

  \(x\)         = 30 : 2

  \(x\)         = 15

x + (-31) - 42 = -45

x - 73 = -45

x = -45 + 73

x = 28

-------

305 - x + 14 = 48 + (x - 23)

319 - x = 48 + x - 23

-x - x = 25 - 319

-2x = -294

x = -294 : (-2)

x = 147

--------

x - 43 = (35 - x) - 48

x = 35 - x - 48 + 43

x + x = 30

2x = 30

x = 30 : 2

x = 15

$x$ + (-31) - (42) = -45

$x$ - (31 + 42) = -45

$x$ - 73 = -45

$x$       = -45 + 73

$x$      = 28

305 - $x$ + 14  = 48 + ($x$ - 23)

(305  + 14) - $x$ = (48 - 23) + $x$

319 - $x$           = 25 + $x$ 

$x$ + $x$              = 319 - 25

2$x$                  = 294

   $x$                 = 294 : 2

   $x$                 = 147

$x-43=\left(35-x\right)$ - 48

$x$ - 43 = 35 - $x$ - 48

$x$ - 43 = - (48 - 35) - $x$

$x$ - 43  = - 13 - $x$

$x$ + $x$    = -13 + 43

2$x$         = 30

  $x$         = 30 : 2

  $x$         = 15

-48+48.(-78)+48.(-21)

=48.(-1-78-21)

=48.-100

=-4800

happy new year

dễ mak bỏ ngoặc ra rùi tính thoy!!

-48+48.(-78)+48.(-21)

=-48.1+48.(-78)+48.(-21)

=48.[(-1)+(-78)+(-21)]

=48.(-100)

=-4800

K mk nha