\(\dfrac{2^{10} \times 13+2^{10} \times 65}{2^{8} \times 104}\)

\(=\dfrac{2^{10} \times (13+65)}{2^{8} \times 2^{2} \times 26}\)

\(=\dfrac{2^{10} \times 78}{2^{10} \times 26}\)

\(=\dfrac{78}{26}=3\)

\(\dfrac{2^{10}\times13+2^{10}\times65}{2^8\times104}\)

=  \(\dfrac{2^{10}\times\left(13+65\right)}{2^8\times104}\)

=  \(\dfrac{2^8\times2^2\times81}{2^8\times104}\)

=  \(\dfrac{2^2\times81}{104}\)

=  \(\dfrac{324}{104}\)

=  \(\dfrac{81}{26}\)

Ta có: \(\dfrac{1}{5}+\dfrac{1}{13}+\dfrac{1}{25}+\dfrac{1}{37}+\dfrac{1}{61}+\dfrac{1}{77}+\dfrac{1}{113}\)

=> \(A=\dfrac{1}{5}+A1\left(\dfrac{1}{13}+\dfrac{1}{25}+\dfrac{1}{37}\right)+A2\left(\dfrac{1}{61}+\dfrac{1}{77}+\dfrac{1}{113}\right)\)

Xét: A1: \(\dfrac{1}{13}< \dfrac{1}{12};\dfrac{1}{25}< \dfrac{1}{12};\dfrac{1}{37}< \dfrac{1}{12}\)

=> \(A1< 3\times\dfrac{1}{12}=\dfrac{1}{4}\)

Xét A2: \(\dfrac{1}{61}< \dfrac{1}{60};\dfrac{1}{77}< \dfrac{1}{60};\dfrac{1}{113}< \dfrac{1}{60}\)

=> \(A2< 3\times\dfrac{1}{60}=\dfrac{1}{20}\)

=> \(A=\dfrac{1}{5}+A1+A2< \dfrac{1}{5}+\dfrac{1}{4}+\dfrac{1}{20}=\dfrac{1}{2}\)

=> \(A< \dfrac{1}{2}\)

=> \(A< B\)

P = 2x³ + 3x2 + 4x + 5

với x = 4 ta có P = 2.4³ + 3x4² + 4x4 + 5 = 128 + 48+16 + 5 =197

Bài `1:`

`A=(a+2b+c)-(a-3b)+(5b+2c)`

`A=a+2b+c-a+3b+5b+2c`

`A=(a-a)+(2b+3b+5b)+(c+2c)`

`A=10b+3c`

~~~~~~~~~~~~~~~~~~~~~~~~

`B=3a-b-(2a-5b+c)+(c-4b)`

`B=3a-b-2a+5b-c+c-4b`

`B=(3a-2a)+(-b+5b-4b)+(-c+c)`

`B=a`

~~~~~~~~~~~~~~~~~~~~~~~

`C=a-2b+(3a+b-4c)-(5a-b+3c)`

`C=a-2b+3a+b-4c-5a+b-3c`

`C=(a+3a-5a)+(-2b+b+b)+(-4c-3c)`

`C=-a-7c`

~~~~~~~~~~~~~~~~~~~~~~~

`D=(2b-3a+c)-(a-4b+2c)-(6b-3a-c)`

`D=2b-3a+c-a+4b-2c-6b+3a+c`

`D=(-3a-a+3a)+(2b+4b-6b)+(c-2c+c)`

`D=-a`

_______________________________________________________

Bài `2:`

`a)332-(681+232)+(431-50)`

`=332-681-232+431-50`

`=(332-232)-(681-431)-50`

`=100-250-50`

`=100-(250+50)=100-300=-200`

~~~~~~~~~~~~~~~~~~~~~~~~~~~

`b)-137.(136-417)-136.(417-137)`

`=-137.136-137.(-417)-136.417-136.(-137)`

`=[-137.136-136.(-137)]+[-137.(-417)-136.417]`

`=-137.(136-136)-417.(-137+136)`

`=-137.0-417.(-1)`

`=0+417=417`

A = (a + 2b + c) - (a - 3b) + (5b + 2c)

   = a + 2b + c - a + 3b + 5 b + 2c

  = a - a + 2b + 3b + 5b + c + 2c

=  10b + 3c

B = 3a - b - (2a - 5b + c) + (c - 4b)

    = 3a - b - 2a + 5b - c + c - 4b

    = 3a - 2a - b + 5b - 4b - c + c

    =  a 

C = a - 2b + (3a +b - 4c) - (5a - b + 3c)

   = a - 2b + 3a + b - 4c - 5a + b - 3c

  = a + 3a - 5a - 2b + b + b - 4c - 3c

 =  - a - 7c

D= ( 2b - 3a + c) - (a - 4b + 2c) - ( 6b - 3a - c) 

  =  2b - 3a + c - a + 4b - 2c -  6b + 3a + c

  =  - 3a - a + 3a + 2b + 4b - 6b + c - 2c + c

 =  - a 

     Số các số lẻ có 2 chữ số:

     (99 - 11) : 2 + 1 = 45 (số)

    Tổng các số lẻ có 2 chữ số:

   (99 + 11) . 45 : 2 = 2475

     Số các số chẵn có 2 chữ số:

  (98 - 10) : 2 + 1 = 45 (số)

Tổng các số chẵn có 2 chữ số:

    (98 + 10) . 45 : 2 = 2430

Hiệu của chúng là: 2475 - 2430 = 45

                       Đáp số:.............

a) 10 = 5 + 5

b)  10 = 0 + 10 = 1 + 9 = 2 + 8 = 3 + 7 = 4 + 6 

A) 5+5=10

B) 10 = 0 + 10 = 1 + 9 = 2 + 8 = 3 + 7 = 4 + 6

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