Bài 2. Tính nhanh
a) 27 + (-2019) + (-27)

= 27 -2019 -27

=(27 - 27) -2019

=0-2019

= -2019

d) (-102) – (345 – 102)

= -102 - 345 +102

= (102 - 102) -345

= 0-345

= -345

b) (-10) + 23 + (-20) + 30

= -10 +23-20+30

= -(10+20) +23 +30

= -30 +23 +30

= (30-30) +23

= 0 +23

= 23

e) (12 + 34 – 56) – (12 – 56)

= 12 +34 -56 -12 +56

= (12-12) + (56-56) +34

= 0+0 +34

= 34

c) (-2).125.(-5).(-8).(+17)

=[(-2) . (-5)] . [ 125.(-8)] . (+17)

= 10 . (-1000).(+17)

= - 10000 . 17

= - 170000

f) 37.(-345) – 345.(-47)

= -345 . (37-47)

= -345.(-10)

=3450

= 102 - ( 345 - 102 -245 )

= 102 - 345 + 102 + 245

= 104

102-[345-(102+245)]=102-2=100

Nhầm 102-[345-(102+245)]=102-(-2)=104

Lời giải:
a. $=13-47-13-59+81+35-13$

$=(13-13-13)-(47+59)+(81+35)$
$=-13-106+116=-13+(116-106)=-13+10=-3$

b.

$=345-61+84+61-116-345$

$=(345-345)+(-61+61)-(116-84)$

$=0+0-32=-32$

a, $(13-47)-(13+59-81)+(35-13)$

$=13-47-13-59+81+35-13$

$=(13-13)+(-47-13)+(-59+81)+35$

$=-60+22+35$

$=-38+35$

$=-3$

$---$

b, $(345-61+84)-(-61+116+345)$

$=345-61+84+61-116-345$

$=(345-345)+(-61+61)+(84-116)$

$=-32$

B) (-11)+350+16+(-350 )

= - 11 + 350 + 16 - 350 )

= ( - 11 + 16 ) + ( 350 - 350 )

= 5 + 0 =5

C) (-10)+23+(-20)+30

= - 10 + 23 - 20 + 30

= ( - 10 - 20 + 30 ) + 23

= - 30 + 30 + 23

= 0 + 23 = 23

D) (456-123)+123

= 456 - 123 + 123 

= 456 

E) (-102)-(345-102)

= - 102 - 345 + 102

= ( - 102 + 102 ) - 345

= 0 - 345

= - 345

F) (12-34)-(34-8)

=  12 - 34  - 34 - 8

= (12 - 8 ) + ( -34 - 34 )

= 4 - 68 

= 64

 G) (12+34-56)-(12-56)

= 12 + 34 - 56 - 12 +56

= ( 12 - 12 ) + ( -56 + 56 ) + 34

= 0 + 0 + 34

= 34

Câu F k giống tính nhanh ____ Có thể là bạn gõ sai đề

@@ Học tốt @@
## Chiyuki Fujito

b ) (-11) + 350 + 16 + (-350) 

= (16 - 11 ) + ( 350 - 350 ) 

= 5 + 0 

= 5 

c)  (-10) + 23 + (-20) + 30

= 23 + ( 30 - 10 - 20 )

= 23 + 0 

= 23

d) ( 456 - 123 ) + 123

= 456 - ( 123 - 123 )

= 456 - 0 

= 456

e)  ( - 102 ) - ( 345 - 102 )

= - 345 - ( 102 - 102 ) 

= - 345 - 0 

= - 345

B) (-11)+350+16+(-350 )

= - 11 + 350 + 16 - 350 )

= ( - 11 + 16 ) + ( 350 - 350 )

= 5 + 0 =5

C) (-10)+23+(-20)+30

= - 10 + 23 - 20 + 30

= ( - 10 - 20 + 30 ) + 23

= - 30 + 30 + 23

a . ( 17x + 23 ) : 12 = 9

=> 17x + 23 = 9 x 12

=> 17x + 23 = 108

=> 17x = 108 - 23

=> 17x = 85

=> x = 5

Vậy x = 5

b . 345 - ( 15x + 63 ) = 102

=> 15x + 63 = 345 - 102

=> 15x + 63 = 243

=> 15x = 243 - 63

=> 15x = 180

=> x = 12

Vậy x = 12

c . ( 11x - 2³ ) . 7³ = 5 . 7⁵

=> ( 11x - 2³ ) . 7³ = 84035

=> ( 11x - 2³ ) . 343 = 84035

=>  11x - 8 = 84035 : 343

= > 11x - 8 = 245

=> 11x = 245 + 8

=> 11x = 253

=> x = 23

Vậy x = 23

Lời giải:

$167(222-345)+345(167+1)-167.345$

$=167.222-167.345+345.167+345-167.345$

$=167.222+(-167.345+167.345)+345-167.345$

$=167.222+345-167.345$

$=167(222-345)+345=167.(-123)+345=-20196$

a) 345 - ( 345 + 77 ) - ( 77 +  23 )

= 345 - 345 - 77  -  77 -  23 

= (345-345) - (77+23) - 77

= 0 - 100 - 77

= -100 - 77

= -177

b) 234 + ( 433 - 234 )

= 234 + 433 - 234

= (234-234) + 433

= 0 + 433

= 433

a) 345 - ( 345 + 77 ) - ( 77 +  23 )

= 345 - 345 - 77 - 77 + 23 = -77 - 77 + 23

= -77.2 + 23

= -154 + 23

= -131

b) 234 + (433 - 234) 

= 234 + 433 - 234

= (234 - 234) + 433

= 0 + 433

= 433

a, 345 - ( 345 + 77 ) - ( 77 + 23 )

= 345 - 345 - 77 - 77 - 23

= - 23

b, 234 + ( 433 - 234 )

= 234 + 433 - 234

= ( 234 - 234 ) + 433

= 433

giải giúp mình nha

\(34500\)

= 345 x ( 75 + 24 ) + 345

= 34500

=345✖(75+1+24)

=345✖10

=3450