\(\dfrac{45.21.25}{7.15.36}=\dfrac{3.3.3.5.7.5.5}{7.5.3.3.2.3.2}=\dfrac{25}{4}\)

45\7 x 21\15 x 25/36

=45x21x25/7x15x36

=15x3x7x3x25/7x15x3x12

=3x25/12

=75/12

=25/4

lx + 12l + 21 = (-7).(-8)

lx + 12l + 21 =  56

lx + 12l         = 56 - 21

lx + 12l         =  35

Suy ra x + 12 = 35 hay x + 12 = -35

TH1: 

x + 12 = 35

x         = 35 - 12

x         = 23

TH2:

x + 12 = -35

x         = -35 - 12

x         = -35 + (-12)

x         =     -47

k mk nha bn,ủng hộ mk nha

a) Vì \(-45< -16\) nên \(\left(-\dfrac{45}{17}\right)^{15}< \left(\dfrac{-16}{17}\right)^{15}\)

b) Vì \(21< 23\) nên \(\left(-\dfrac{8}{9}\right)^{21}< \left(-\dfrac{8}{9}\right)^{23}\)

c) \(27^{40}=3^{3^{40}}=3^{120}\)

\(64^{60}=8^{2^{60}}=8^{120}\)

Vì \(3< 8\) nên \(3^{120}< 8^{120}\) hay \(27^{40}< 64^{60}\)

con ai kooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo

co don quaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

Bạn nên gõ hẳn câu bạn muốn trợ giúp. Nếu không, hãy chụp đề một cách rõ ràng. Không chụp quá nhiều bài trong 1 post nhé. Như vậy khả năng nhận được trợ giúp của bạn sẽ cao hơn.

a) 41. 36+ 59. 90 + 41. 84 + 59. 30

= 41 . (36 + 84) + 59 . (90 + 30)

= 41 . 120 + 59 . 120

= 120 . ( 41 + 59 )

= 120 . 100

= 12000

b) 4. 51 . 7 + 2 . 86 .7 + 6 . 4 . 7

= 28 . 51 + 2 . 43 . 2 . 7 + 6 . 4 . 7

= 28 . 51 + 28 . 43 + 28 . 6

= 28 . ( 51 + 43 + 6 )

= 28 . 100

= 2800

c) ( 4.7 ) . 5 + ( 4.7 ) . 43 + ( 4.7) - 6

= 28 . 5 + 28 .43 + 28 - 6

= 28 . (5 + 43 + 1) - 6

= 28 . 49 - 6

= 1372 - 6

= 1366.

d) 53 . 39 + 47 . 39 - 53 . 21 - 47 . 21

= 53 . (39 - 21) + 47. (39 - 21)

= (39 - 21) . ( 53 + 47 )

= 18 . 100

= 1800.

a) \(-\left(76-35+15\right)+\left[18-27+\left(-17\right)\right]\)

\(=-76+35+15+18-27-17\)

\(=-52\)

b) \(167+\left[127-235-\left(-16\right)\right]+\left(-67\right)\)

\(=167+127-235+16-67\)

\(=8\)

c) \(\left(-19\right)+165-\left[27+\left(-21\right)-\left(+72\right)\right]\)

\(=\left(-19\right)+165-27+21+72\)

\(=212\)

d) \(89.\left(-2\right)+\left[20+\left(-2\right).\left(-5\right)-85\right]\)

\(=\left(-178\right)+\left(20+10-85\right)\)

\(=\left(-178\right)+20+10-85\)

\(=-233\)

Bài 21

1 are

2 enjoy reading

3 loves reading 

4 learns

5 ;oles

6 spends

7 thinks 

8talks

9 lasts

10 agree

11 will go

12 will be

13 will buy

14 will be

15 will probably join

16 have

17 will go

18 enjoy

a) Yes, they do

b) Because there are many interesting things

c) They talk about the books

d) Tomorrow

e) they will go home and enjoy their books

\(21,\\ b,ĐK:x\ge1\\ PT\Leftrightarrow\sqrt{x-1-2\sqrt{x-1}+1}=2\\ \Leftrightarrow\sqrt{\left(\sqrt{x-1}-1\right)^2}=2\\ \Leftrightarrow\left|\sqrt{x-1}-1\right|=2\\ \Leftrightarrow\left[{}\begin{matrix}\sqrt{x-1}-1=2\\1-\sqrt{x-1}=2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=10\left(tm\right)\\\sqrt{x-1}=-1\left(ktm\right)\end{matrix}\right.\\ \Leftrightarrow x=10\)