Áp dụng công thức này là được :

m.a+m.b+m.c = m(a+b+c)

a) 58.75 + 58.50 - 58.25

= 58. (75 + 50 - 25)

= 58. 100

= 5800

b) 27.39 + 27.63 + 2.27

= 27. (39 + 63 - 2)

= 27. 100

= 2700

c) 128.46 + 128.32 + 128.22

= 128.(46 + 32 + 22)

= 128. 100

= 12800

d) 12.35 + 35.182 - 35.94

= 35.(12 + 182 - 94)

= 35. 100

= 3500

e) 48.19 + 48.115 + 134.52

= 48.(19 + 115) + 134.52

= 48.134 + 134.52

= 134.(48 + 52)

= 134.100

= 13400

f) 136.23 + 136.17 - 40.36

= 136.(23 + 17) - 40.36

= 136.40 - 40.36

= 40.(136 - 36)

= 40.100

= 4000

g) 17.93 + 116.83 + 17.23

= 17.(93 + 23) + 116.83

= 17.116 + 116.83

= 116.(17 + 83)

= 116.100

= 11600

h) 19.27 + 47.81 + 19.20

= 19.(27 + 20) + 47.81

= 19.47 + 47.81

= 47.(19 + 81)

= 47.100

= 4700

i) 87.23 + 13.93 + 70.87

= 87.(23 + 70) + 13.93

= 87.93 + 13.93

= 93.(87 + 13)

= 93.100

= 9300

#NgHn

a,

58.75 + 58.50 - 58.25

= 58.(75 + 50 - 25)

= 58. (125 - 25)

= 58.100

 = 5800

b, 27.39 + 27.63 - 2.27

= 27.(39 + 63 - 2)

= 27.(102 - 2)

= 27.100

= 2700 

Đấu chấm là phẩy hay nhân

58(75+50-25.34)=58.(-725)=-42050

a,58.75 + 58.50 - 58.25

= 58.(75 + 50 - 25)

= 58.100

= 5800                                            

b,27.39 + 27.63 - 2.27

= 27.(39 + 63 - 2)

= 27.100

= 2700                                               

c,128.46 + 128.32 + 128.22

= 128.(46 + 32 + 22)

= 128.100

= 12800                                       

d,66.25 + 5.66 + 66.14+ 33.66

= 66.(25 + 5 + 14 + 33)

= 66.77

= 5082                                  

i,2+5+11+...+47+65

= 2+5+11+23+47+65

= (65+5) + (23+47) + (2+11)

= 70 + 70 + 13

= 70.2 + 13

= 140 + 13

= 153

 e,48.19 + 48.115+134.5

= 48.(19 + 115) + 134.5

= 48.134 + 134.5

= 134.(48 + 5)

= 134.53

=7102

f,125.98 - 125.46 - 52.25

= 125.(98 - 46) - 52.25

= 125.52 - 52.25

= 52.(125 - 25)

= 52.100

= 5200

g,136.23 + 136.17 - 40.36

= 136.(23 + 17) - 40.36

= 136.40 - 40.36

= 40.(136 - 36)

= 40.100

= 4000

h,1+2+3+4+5+...+n

\(=\frac{n\left(n+1\right)}{2}\)

2 . Tính nhanh   

a) 58. 75 + 58 . 50 - 58 . 25 

= 58 . ( 75 + 50 - 25 )

= 58 . 100

= 5 800

b) 27 . 39 + 27 . 63 - 2 . 27

= 27 . ( 39 + 63 - 2 )

= 27 . 100

= 2 700

c) 128 . 46 + 128 . 32 + 128 . 22 

= 128 . ( 46 + 32 + 22 )

= 128 . 100

= 12 800

d) 66 . 25 + 5 . 66 + 66 . 14 + 33 . 66 

= 66 . ( 25 + 5 + 14 + 33 )

= 66 . 77

= 5082 

e) 48 . 19 + 48 . 115 + 134 . 5 

= 48 . ( 19 + 115 ) + 134 . 5 

= 48 . 134 + 134 . 5 

= 134 . ( 48 + 5 )

= 134 . 53 

= 7102 

f, 125 . 98  - 125 . 46 - 52 . 25 

= 125 . ( 98 - 46 ) - 52 . 25 

= 125 . 52 - 52 . 25 

= 52 . ( 125 - 25 )

= 52 . 100

= 5 200

g, 136 . 23 + 136 . 17 - 40 . 36 

= 136 . ( 23 + 17 ) - 40 . 36 

= 136 . 40 - 40 . 36 

= 40 . ( 136 - 36 )

= 40 . 100

= 4 000

Bài 1

a) (3x - 2⁴).7³ = 2.7⁴

3x - 16 = 2.7⁴ : 7³

3x - 16 = 2.7

3x - 16 = 14

3x = 14 + 16

3x =30

x = 30 : 3

x = 10

b) x - [42 + (-28)] = -8

x - 14 = -8

x = -8 + 14

x = 6

c) 4 - 7.x = x - (13 - 4)

x + 7x = 4 + 9

8x = 13

x = 13/8

Bài 1: a,   (3\(x\) - 2⁴ ).7³ = 2.7⁴

                3\(x\) - 2⁴    = 2.7⁴ : 7³

                3\(x\)  - 16   = 14

                 3\(x\)           = 30 

                    \(x\)          = 10

b, \(x\) - (42 + (-28) ] = -8

    \(x\) - 14 = -8

    \(x\)        = 14 - 8

    \(x\)        = 6

c, 4 - (7\(x\)) = \(x\) - (13 - 4)

   4 - 7\(x\)   = \(x\) - 9

        \(x\) + 7\(x\) = 4 + 9

          8\(x\)     = 13

             \(x\)    = \(\dfrac{13}{8}\)

\(A=8\cdot17\cdot125=\left(125\cdot8\right)\cdot17=1000\cdot17=17000\)

\(B=\left(25\cdot4\right)\cdot37=100\cdot37=3700\)

\(C=\left(75+50-25\right)\cdot58=100\cdot58=5800\)

\(D=\left(39+63-2\right)\cdot27=100\cdot27=2700\)

A=8.17.125= (8.125).17= 1000.17=17000

b=4.37.25=(4.25).37=100.37=3700

c= 58.75+58.50-58.25= 58.(75+50 - 25)= 58.100=5800

d=27.39+27.63-2.27= 27.(39+63-2)=27.100=2700

128.46 + 128.32 + 128.22

=128.(46+32+22)

=128.100=12800

K mk nha, mk k lại

128.46+128.32+128.22=128.(46+32+22)

                                     =128.100

                                     =12800