Trả lời

Số tự nhiên a có chia hết cho 2.

Chắc z !

-Số a ít nhất là 58

    - Vậy:

-Số a có chia hết cho 2

-Số a không chia hết cho 4

\(A=2+2^2+2^3+2^4+2^5+2^6+2^7+2^8+2^9+2^{10}\)

\(A=\left(2+2^2\right)+\left(2^3+2^4\right)+\left(2^5+2^6\right)+\left(2^7+2^8\right)+\left(2^9+2^{10}\right)\)

\(A=2\left(1+2\right)+2^3\left(1+2\right)+2^5\left(1+2\right)+2^7\left(1+2\right)+2^9\left(1+2\right)\)

\(A=2\cdot3+2^3\cdot3+2^5\cdot3+2^7\cdot3+2^9\cdot3\text{ }⋮\text{ }3\)

\(A=2+2^2+2^3+2^4+2^5+2^6+2^7+2^8+2^9+2^{10}\)

\(A=\left(2+2^2\right)+\left(2^3+2^4\right)+\left(2^5+2^6\right)+\left(2^7+2^8\right)+\left(2^9+2^{10}\right)\)

\(A=2\left(1+2\right)+2^3\left(1+2\right)+2^5\left(1+2\right)+2^7\left(1+2\right)+2^9\left(1+2\right)\)

\(A=2\cdot3+2^3\cdot3+2^5\cdot3+2^7\cdot3+2^9\cdot3\)

\(\Rightarrow\text{ }A\text{ }⋮\text{ }3\text{ }\left(\text{ ĐPCM}\right)\)

câu 1:

3.(x+2) + 5x = 22

=> 3x + 6 + 5x = 22

=> 8x = 22 - 6 = 16

=> x = 16/8 = 2

câu 2:

2(x + 1) + 5(x + 2) = 61

=> 2x + 2 + 5x + 10 = 61

=> 7x + 12 = 61

=>7x = 61 - 12 = 49

=> x = 49/7 = 7

hok tốt

# kiseki no enzeru #

C1:

3( x + 2 ) + 5x = 22

3x + 6 + 5x     = 22

3x + 5x           = 22 - 6

8x                   = 16

x                     = 16 : 8

x                     = 2

C2: 

2( x + 1 ) + 5( x +2 ) = 61

2x + 2 + 5x + 10      = 61

2x + 5x                     = 61 - 2 - 10

7x                             = 49

x                               = 49 : 7

x                               = 7

~ Hok tốt ~

1) Ta có : 72⁴⁵ - 72⁴³ = 72⁴³.(72² - 1)

               72⁴⁴ - 7⁴² = 7⁴².(72² - 1)

Vì 72⁴³ > 72⁴²

=> 72⁴³.(72² - 1) > 7⁴².(72² - 1)

=> 72⁴⁵ - 72⁴³ >  72⁴⁴ - 7⁴² 

2)  Giải

\(M=\frac{1}{4}+\frac{1}{4^2}+\frac{1}{4^3}+....+\frac{1}{4^{50}}\)

\(4M=1+\frac{1}{4}+\frac{1}{4^2}+...+\frac{1}{4^{49}}\)

Lấy 4M trừ M theo vế ta có :

\(4M-M=\left(1+\frac{1}{4}+\frac{1}{4^2}+...+\frac{1}{4^{49}}\right)-\left(\frac{1}{4}+\frac{1}{4^2}+\frac{1}{4^3}+...+\frac{1}{4^{50}}\right)\)

\(3M=1-\frac{1}{49}\)

  \(M=\left(1-\frac{1}{49}\right):3\)

        \(=\frac{1}{3}-\frac{1}{147}< \frac{1}{3}\)

Vậy \(M< \frac{1}{3}\left(\text{đpcm}\right)\)

Quickly please

https://olm.vn/hoi-dap/detail/215935065792.html

Xem tại link này (mình gửi cho)

Học tốt!!!!!!!!!!!!!!!!  :)