phép tính này có quy tắc :

nhân chia trước, cộng trừ sau.

trong ngoặc trc ngoài ngoặc sau

tíc mình nha

(42 x 43 + 43 x 57 + 43) - 360 : 4

= 4426549 - 360 : 4

= 4426549 - 90

= 4426459

(372 - 19 x 4 +  (981 : 9 - 13)

= 296         +         96

= 392

456  : 2 x 18 + 456 : 3 - 102

= 4104         +             50

=  4154

>_< học tốt

(42*43+43*57+43)-360:4 

=42*43+43*57+43*1 -360:4

= 43*(42+57+1)-360:9

=43*100-90

a) \(\left(42\times43+43\times57+43\right)-360:4\)

\(=43\times\left(42+57+1\right)-90\)

\(=43\times100-90\)

\(=4300-90\)

\(=4210\)

b) \(\left(372-19\times4\right)+\left(981:9-13\right)\)

\(=\left(4\times93-19\times4\right)+\left(109-13\right)\)

\(=4\times\left(93-19\right)+109-13\)

\(=4\times74+109-13\)

\(=296+109-13\)

\(=392\)

c) \(456:2\times18+456:3-102\)

\(=456\times\frac{1}{2}\times18+456\times\frac{1}{3}-102\)

\(=456\times\left(\frac{1}{2}\times18+\frac{1}{3}\right)-102\)

\(=456\times\left(9+\frac{1}{3}\right)-102\)

\(=456\times\frac{28}{3}-102\)

\(=4256-102\)

\(=4154\)

ko bk tính nhanh!

a)( 42 x 43 + 57+43 ) - 360 :4                                                 b) (372 - 19 x 4 ) + ( 981 : 9 - 13 )

  = 43 x (42 + 57 +1 ) - 90                                                       = (372 - 76 )  + ( 109 - 13) 

  = 43 x 100 - 90                                                                     = 296 + 96   

  = 4300 - 90                                                                          = 392   

  = 4210

a. 64 x 25 + 35 x 25 + 25

= 64 x 25 + 35 x 25 + 25 x 1

= 25 x ( 64 + 35 + 1 )

= 25 x 100 

= 2500

b. 58 x 42 + 32 x 8 + 5 x 16

c. ( 42 x 43 + 57 x 43 + 43 ) - 360 : 4

= 42 x 43 + 57 x 43 + 43 x 1 - 90

= 43 x ( 42 + 57 +1 ) - 90

= 43 x 100 - 90

= 4300 - 90

= 4210

d. 456 : 2 x 181456 : 3 - 102

Trả lời:

a,\(64\times25+35\times25+25\)

\(=25\times\left(64+35+1\right)\)

\(=25\times100\)

\(=2500\)

b,\(58\times42+32\times8+5\times16\)

\(=2436+256+80\)

\(=2772\)

c,\(\left(42\times43+57\times43+43\right)-360\div4\)

\(=43\times\left(42+57+1\right)-90\)

\(=43\times100-90\)

\(=4300-90\)

\(=4210\)

d,\(456\div2\times181456\div3-102\)

\(=228\div3\times181456-102\)

\(=76\times181456-102\)

\(=13790656-102\)

\(=13790554\)

a,64 x 25 + 35 x 25 +25

=25x(64+35+1)

=25x100

=250

b, 58 x 42 +32 x 8 +5 x 16

=2772

c,(42 x 43 +57 x 43+43 )-360:4

=43x(42+57+1) - 360 :4

= 43 x 100 -90

=4300-90

=4210

d,456:2 x 181456:3 -102

=228x181456:3-102

=13790656-102

=13790554

\(\text{1/ (2x - 5) +17 =6}\\ 2x-5=6-17\\ 2x-5=-11\\ 2x=-11+5\\ x=-6:2\\ x=-3\)

\(2x-5=-11\Leftrightarrow x=-3\)

\(\text{2/ 10 - 2(4 - 3x) = - 4}\\ 2\left(4-3x\right)=10-\left(-4\right)\\ 2\left(4-3x\right)=14\\ 4-3x=14:2\\ 4-3x=7\\ 3x=4-7\\ x=-3:3\\ x=-1\)

= [43 x ( 42 + 57 + 1)] - 90

= (43 x 100) -90

= 4300 - 90

= 4210

a,( 42 x 43 + 43 x 57 + 43 ) - 360 : 4

= [ 43 x ( 42 + 57 + 1 ) ] - 90

= [ 43 x 100 ] - 90 

= 4300 - 90

= 4210

b, 372 - 19 x 4 - 981 : 9 - 13

 = 372 - 76 - 109 - 13

= 174

c, 452 : 2 x 18 - 456 : 3  - 102

 = 226 x 18 - 152 - 102

 = 4068 - 152 - 102

 = 3814

a. ( 42 x 43 + 43 x 57 + 43 ) - 360 : 4                     b. 372 - 19 x 4 - 981 : 9 - 13

  = ( 42 x 43 + 43 x 57 + 43 x 1 ) - 360 : 4                 = 372 - 76  - 109  - 13

  = ( 43 x ( 42 + 57 + 1 ) ) - 360 : 4                            = 296 - 109 - 13

  = ( 43 x      100   )  - 360 : 4                                   =  187 - 13

  =     4300 - 360 : 4                                                = 174

  =      4300 - 90

  =  4210

c. 456 : 2 x 18 - 456 : 3 - 102

  =   228  x 18 - 152 - 102

 =    4104 - 152 - 102

= 3952 - 102

=  3850

(42 x 43 + 43 x 57 + 43) - 360 : 4

=(42 x 43 +43 x 57 + 43 x 1) - 360 : 4

= 43 x (42 + 57 + 1) - 360 :4

=43  x 100 - 360 : 4

=4300 - 90

=4210

b 456 : 2 x 18 + 456 :3 -102

=456 x (18:2) + 456 :3 -102

=456 x 9 + 456 : 3 - 102

=5154 +102 - 102 

=5154+0 

=5154

bai 2 :

gọi số cần tìm là ab

ta có : 5ab =26ab

500 +ab =26ab

25ab =500ab

ab=500:25

ab =20

\(a,\frac{x+1}{65}+\frac{x+2}{64}=\frac{x+3}{63}+\frac{x+4}{62}\)

\(\Rightarrow\left[\frac{x+1}{65}+1\right]+\left[\frac{x+2}{64}+1\right]=\left[\frac{x+3}{63}+1\right]+\left[\frac{x+4}{62}+1\right]\)

\(\Rightarrow\frac{x+1+65}{65}+\frac{x+2+64}{64}=\frac{x+3+63}{63}+\frac{x+4+62}{62}\)

\(\Rightarrow\frac{x+66}{65}+\frac{x+66}{64}=\frac{x+66}{63}+\frac{x+66}{62}\)

\(\Rightarrow\frac{x+66}{65}+\frac{x+66}{64}=\frac{x+66}{63}+\frac{x+66}{62}=0\)

\(\Rightarrow\left[x+66\right]\left[\frac{1}{65}+\frac{1}{64}-\frac{1}{63}+\frac{1}{62}\right]=0\)

Mà \(\frac{1}{65}+\frac{1}{64}-\frac{1}{63}+\frac{1}{62}\ne0\)

\(\Rightarrow x+66=0\)

\(\Rightarrow x=0-66=-66\)

Auto làm nốt câu b

a,  Cộng cả 2 vế với 2 

Ta có \(\frac{x+1}{64}+\frac{x+2}{63}+2=\frac{x+3}{62}+\frac{x+4}{61}+2\)

\(\left(\frac{x+1}{64}+\frac{64}{64}\right)+\left(\frac{x+2}{63}+\frac{63}{63}\right)=\left(\frac{x+3}{62}+\frac{62}{62}\right)+\left(\frac{x+4}{61}+\frac{61}{61}\right)\)

=>  \(\frac{x+65}{64}+\frac{x+65}{63}=\frac{x+65}{62}+\frac{x+65}{61}\)\(\)

=> \(\frac{x+65}{64}+\frac{x+65}{63}-\frac{x+65}{62}-\frac{x+65}{61}=0\)

=> \(\left(x+65\right)\left(\frac{1}{64}+\frac{1}{63}-\frac{1}{62}-\frac{1}{61}\right)=0\)

Do \(\frac{1}{64}+\frac{1}{63}-\frac{1}{62}-\frac{1}{61}\ne0\)=> \(x+65=0\)

=> \(x=-65\)

b ,  Lm tương tự như Câu a

Chúc bn hok tốt

a) \(\frac{x+1}{65}+\frac{x+2}{64}=\frac{x+3}{63}+\frac{x+4}{62}\)

\(\Leftrightarrow\frac{x+1}{65}+\frac{x+2}{64}+2=\frac{x+3}{63}+\frac{x+4}{62}+2\)

\(\Leftrightarrow\left(\frac{x+1}{65}+1\right)+\left(\frac{x+2}{64}+1\right)=\left(\frac{x+3}{63}+1\right)+\left(\frac{x+4}{62}+1\right)\)

\(\Leftrightarrow\frac{x+1+65}{65}+\frac{x+2+64}{64}=\frac{x+3+63}{63}+\frac{x+4+62}{62}\)

\(\Leftrightarrow\frac{x+66}{65}+\frac{x+66}{64}=\frac{x+66}{63}+\frac{x+66}{62}\)

\(\Leftrightarrow\frac{x+66}{65}+\frac{x+66}{64}-\frac{x+66}{63}-\frac{x+66}{62}=0\)

\(\Leftrightarrow\left(x+66\right)\left(\frac{1}{65}+\frac{1}{64}-\frac{1}{63}-\frac{1}{62}\right)=0\)

\(\Leftrightarrow x+66=0\)

\(\Leftrightarrow x=-66\)

CÂu b) làm tương tự:

- Trừ 3 cho hai vế ( câu a) mk cộng 2 cho hai vế)

- Tách -3 = -1-1-1 rồi kết hợp với mỗi hạng tử

CỐ LÊN NHÉ

NẾU bạn KHÔNG HIỂU thì câu b) mik sẽ làm kĩ càng và rõ ràng hơn cho bạn hiểu

x + ( - 45 ) = ( - 62 ) + 17

x + ( - 45 ) = - 45

x              = - 45 - ( - 45 ) = - 45 + 45

x              = 0

x + 29 = ( - 43 ) + ( - 43 )

x + 29 = - 86

x         = - 86 - 29

x         = - 115

a)>

b)<

c)=