2 . 2³ + 3 . 2⁴ + 4 . 2⁵ + ... + n . 2ⁿ⁺¹ = 2ⁿ⁺⁶

Đề như này hả?

 uk đúng r bn

   234 - ( 56 + 24 : 4 )
=234 - ( 56 + 6 )
=234 - 62
=172
 

  100 : { 250 : [ 450 - ( 500 - 2² . 25) ] }
=100 : { 250 : [ 450 - ( 500 - 4 . 25) ] }
=100 : { 250 : [ 450 - ( 500 - 100) ] }
=100 : { 250 :  [ 450 - 400] }
=100 : { 250 : 50}
=100 : 5
=20

$B=\dfrac{4^5\cdot10\cdot5^6+25^5\cdot2^8}{2^8\cdot5^4+5^7\cdot2^5}$

$=\dfrac{2^{10}\cdot2\cdot5\cdot5^6+5^{10}\cdot2^8}{2^8\cdot5^4+2^5\cdot5^7}$

$=\dfrac{2^{11}\cdot5^7+2^8\cdot5^{10}}{2^8\cdot5^4+2^5\cdot5^7}$

$=\dfrac{2^8\cdot5^7(2^3+5^3)}{2^5\cdot5^4(2^3+5^3)}$

$=2^{8-5}\cdot5^{7-4}$

$=2^3\cdot5^3$

$=8\cdot125$

$=1000.$

dễ, nhưng phai giai dc câu nay  60% nhan x cong 2 phan 3 = 1 phan 3 nhan 6va 1 phan 3

dễ mà

Bài giải:

a)1³+2³

=1+8

=9

Vậy 1³+2³ là số chính phương.

b)1³+2³+3³

=1+8+27

=36

Vậy 1³+2³+3³ là số chính phương.

c)1³+2³+3³+4³

=1+8+27+64

=100

Vậy 1³+2³+3³+4³ là số chính phương.

Thank you and study well!

Hbioghgjgh

$\textbf{a)}$

$2^n\cdot2^4=128$

$\Leftrightarrow2^{n+4}=2^7$

$\Leftrightarrow n+4=7$

$\Leftrightarrow n=3.$

$\textbf{A)}$

$A=\left(2^{\,2^{6n+2}}+3\right):7.$

Ta có: $2^3\equiv1\pmod7.$

Lại có $6n+2\ge2\Rightarrow2^{6n+2}$ chia hết cho $4$, nên $2^{6n+2}\equiv1\pmod3.$

Suy ra $2^{2^{6n+2}}\equiv2^1\equiv2\pmod7.$

Vậy $2^{2^{6n+2}}+3\equiv2+3\equiv5\pmod7.$

$\Rightarrow$ Số dư là $5$.

$\textbf{B)}$

$B=\left(2^{\,2^{3n+1}}+3\right):13.$

Ta có: $2^{12}\equiv1\pmod{13}.$

Lại có $2^{3n+1}=2\cdot8^n.$

Vì $8^2\equiv12,\;8^3\equiv5,\;8^4\equiv1\pmod{12}$ nên $8^n\equiv4\pmod{12}$ khi $n\equiv2\pmod4$, do đó $2^{3n+1}\equiv8\pmod{12}.$

Suy ra $2^{2^{3n+1}}\equiv2^8\equiv256\equiv9\pmod{13}.$

Vậy $2^{2^{3n+1}}+3\equiv9+3\equiv12\pmod{13}.$

$\Rightarrow$ Số dư là $12$.

$\textbf{A)}$

$A=\left(2^{\,2^{6n+2}}+3\right):7.$

Ta có: $2^3\equiv1\pmod7.$

Lại có $6n+2\ge2\Rightarrow2^{6n+2}$ chia hết cho $4$, nên $2^{6n+2}\equiv1\pmod3.$

Suy ra $2^{2^{6n+2}}\equiv2^1\equiv2\pmod7.$

Vậy $2^{2^{6n+2}}+3\equiv2+3\equiv5\pmod7.$

$\Rightarrow$ Số dư là $5$.

$\textbf{B)}$

$B=\left(2^{\,2^{3n+1}}+3\right):13.$

Ta có: $2^{12}\equiv1\pmod{13}.$

Lại có $2^{3n+1}=2\cdot8^n.$

Vì $8^2\equiv12,\;8^3\equiv5,\;8^4\equiv1\pmod{12}$ nên $8^n\equiv4\pmod{12}$ khi $n\equiv2\pmod4$, do đó $2^{3n+1}\equiv8\pmod{12}.$

Suy ra $2^{2^{3n+1}}\equiv2^8\equiv256\equiv9\pmod{13}.$

Vậy $2^{2^{3n+1}}+3\equiv9+3\equiv12\pmod{13}.$

$\Rightarrow$ **Số dư là $12$.**

sao ko dung f(x) ma viet

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

a=\(\left(2+2^2\right)+2^2.\left(2+2^2\right)+..+2^8\left(2+2^2\right)\)

a=\(\left(2+2^2\right).\left(1+2^2+..+2^8\right)\)

a=\(6.\left(1+2^2+2^4+2^6+2^8\right)\)

chia het cho 3