a) 20/19 > 21/20 

b) 12/129 < 21/172 

c) 63/81 < 103/135

d) -101/506 > -707/3534

a) 30x-3x = 5 . 54

=> 27x = 270

=> x = 10

b) 15x-9x + 2x = 7

=> 8x = 7

\(\Rightarrow x=\dfrac{7}{8}\)

30x - 3x = 5 . 54

= x . ( 30 - 3 ) = 270

= x .27 = 270

= x = 270 : 27

= x = 10

15x - 9x + 2x = 7

= x . ( 15 - 9 + 2 ) = 7

= x . 8 = 7

= x = 7/8

a,${5.2}^2$$-18:3^2$

$=5.4-18:9$

$=20-2$

$=18$

$\mathrm{cho\; mình\; tick\; nha}$

5.\(2^2\)-18:3

=5.4-18:3

=20-6

=14

Đặt A = \(\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2022}}\)

\(\Rightarrow2.A=\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2022}}+\dfrac{1}{2^{2023}}\)

\(\Rightarrow2.A-A=\left(\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2022}}+\dfrac{1}{2^{2023}}\right)-\left(\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2022}}\right)\)

\(\Rightarrow A=\dfrac{1}{2^{2023}}-\dfrac{1}{2}\)

S = 1 + 1  + 1  + ...... + 1      < 1 
      2   2^2  2^3           2^20 

2S = 1 + 1 + 1  + ...... + 1 
              2   2^2           2^19 

2S - S = 1 - 1
                2^20
S = 1 - 1      < 1
          2^20

=> S < 1

      30x - 3x = 25

<=> 27x = 25 

<=> x= 25/27

30x- 3x= 25
27x      = 25
    x      = \(\dfrac{25}{27}\)

\(2^8\) và \(3^5\)

=4 và 243

vì 4< 243

nên \(2^{^{ }8}\) < \(3^5\)

Ta có : 2⁸ = 256                        3⁵ = 243

Vì 256 > 243 nên 2⁸ > 3⁵

Ta có : 10³⁰ = 10^3.10 = ( 10³ )¹⁰ = 1000¹⁰

2¹⁰⁰ = 2^10.10= ( 2¹⁰ )¹⁰ = 1024¹⁰

Vì 1000¹⁰ < 1024¹⁰ nên 10³⁰ < 2¹⁰⁰

     57 + 3.(37-4x)=96

<=> 3.(37-4x)=39

<=> 37 - 4x = 13

<=> 4x = 24 

<=> x = 6

57 + 3 . ( 37 - 4x ) = 96

=> 3 . ( 37 - 4x ) = 39

=> 37 - 4x = 13

=> 4x = 24

=> x = 6

17.85+15.77-120

=1445+255-120

=1700-120

=1580

mik làm lại ạ 

= 1445+1155-120

=2600-120

=2480

32.47+52.53-200

= ( 52 - 20 ).47+52.53-200

= 52 . 47 - 20 . 47 + 52.53 - 20 . 10

= 52.(47+53) - 20.(47-10)

= 52 . 100 - 20 . 37

= 5200 - 740

= 4460

32.47+52.53-200

= ( 52 - 20 ).47+52 . 53 -  200

= 52 . 47 - 20 . 47 + 52 . 53 - 20 . 10

= 52.(47+53) - 20.(47-10)

= 52 . 100 - 20 . 37

= 5200 - 740

= 4460

217 - 17 x X = 200

=> 17 x X = 217 - 200 = 17

=> X = 17 : 17 = 1

X = 1