a)\(\frac{25.4-0,5\cdot40\cdot0,2\cdot20\cdot0,25}{1+2+8+...+129+156}\)

\(=\frac{100-100}{1+2+8+...+156}\)

\(=\frac{0}{1+2+8+...+156}\)

\(=0\)

b)\(\frac{0,5\cdot40-0,5\cdot20\cdot8\cdot0,1\cdot0,25\cdot10}{128:8.16.4\left(4+52:4\right)}=\frac{20-20}{128:8.16.4.\left(4+52:4\right)}=\frac{0}{128:8.16.4.\left(4+52:4\right)}=0\)

a) 48 x 9 - 48 x 8

= 48 x (9 - 8)

= 48 x 1

= 48

b) 156 x 7 - 156 x 2

= 156 x (7 - 2)

= 156 x 5

= 780

(129,3 - 60,8 ) x 5,2 + 143,8  = 500

Bài 1:

a. 

$-12-(-46)=-12+46=46-12=34$

b.

$-(-8)-54=8-54=-(54-8)=-46$

c.

$-15-(-72)=-15+72=72-15=57$

Bài 2:

a. $(156-812)-(156-12)=156-812-156+12$

$=(156-156)-(812-12)=0-800=-800$

b.

$-(-72+83)-(72+17)=72-83-72-17=(72-72)-(83+17)$

$=0-100=-100$

c.

$-(-23-78)+(77-178)=23+78+77-178$

$=(23+77)-(178-78)=100-100=0$

d.

$(-213-156)-(-213+44)=-213-156+213-44=(-213+213)-(156+44)$

$=0-200=-200$

2.(1+2+3+4+...+x)=156

1+2+3+4+...+x=78

đáp số là 24/2=12

x=15 bn nhé

5/6 + 7/12 = 10/12 + 7/12 = 17/12

9/16 - 3/8 = 9/16 - 6/16 = 3/16

11/10 + 3/5 : 2/3 =11/10 + 3/5 x 3/2 = 11/10 + 9/10 = 20/10 = 2

\(\dfrac{5}{6}+\dfrac{7}{12}=\dfrac{10}{12}+\dfrac{7}{12}=\dfrac{17}{12}\)

\(\dfrac{9}{16}-\dfrac{3}{8}=\dfrac{9}{16}-\dfrac{6}{16}=\dfrac{3}{16}\)

\(\dfrac{11}{10}+\dfrac{3}{5}:\dfrac{2}{3}=\dfrac{11}{10}+\dfrac{3}{5}\times\dfrac{3}{2}=\dfrac{11}{10}+\dfrac{9}{10}=\dfrac{20}{10}=2\)

5/6 + 7/12

= 10/12 + 7/12

= 17/12 

9/16 - 3/8

= 9/16 - 6/16

= 3/16 

11/10 + 3/5 : 2/3

= 11/10 + ( 3/5 : 2/3 )

= 11/10 + ( 3/5 x 3/2 )

= 11/10 + 9/10

= 20/10 = 2.

Lời giải:

a. < 

b. > 

c. <

=> (2+2x)[(2x-2)/2+1]/2=156

=>2(x+1)x/2=156

=>x(x+1)=156

=>x(x+1)=12.13

=>x=12

`136 -4^2 : x=134`

`=> 136-16:x=134`

`=> 16:x= 136-134`

`=> 16:x=2`

`=>x=16:2`

`=>x=8`

__

`19-5(x-1)=4`

`=> 5(x-1)=19-4`

`=> 5(x-1) =15`

`=> x-1=15:5`

`=>x-1=3`

`=>x=3+1`

`=>x=4`

__

`257-(x^2-1) =177`

`=>x^2-1=257-177`

`=>x^2-1=80`

`=>x^2=80+1`

`=>x^2=81`

`=>x^2=(+- 9)^2`

`=> x= +- 9`

__

`(x^2-17) : 8=2^3`

`=> x^2 -17 = 8 * 8`

`=> x^2 -17= 64`

`=> x^2 =64+17`

`=>x^2=81`

`=>x^2=(+- 9)^2`

`=> x= +- 9`

136 - 4² : x = 134

4² : x = 136 - 134

8 : x = 2

x = 8 : 2

x = 4

--------

129 - 5(x - 1) = 4

5(x - 1) = 129 - 4

5(x - 1) = 125

x - 1 = 125 : 5

x - 1 = 25

x = 25 + 1

x = 26

------------

257 - (x² - 1) = 177

x² - 1 = 257 - 177

x² - 1 = 80

x² = 80 + 1

x² = 81

x = -9 hoặc x = 9

--------

(x² - 17) : 8 = 8

x² - 17 = 8 . 8

x² - 17 = 64

x² = 64 + 17

x² = 81

x = -9 hoặc x = 9