`@` `\text {Ans}`

`\downarorw`

`2^x \div 2 = 128?`

`=> 2^x = 128 * 2`

`=> 2^x = 256`

`=> 2^x = 2^8`

`=> x = 8`

Vậy, `x = 8`

______

`4^x \div 4^3 = 16`

`=> 4^x = 16 * 4^3`

`=> 4^x = 4^2 * 4^3`

`=> 4^x = 4^5`

`=> x = 5`

Vậy, ` x = 5`

________

`12^x \div 3 = 48 ?`

`=> 12^x = 48 * 3`

`=> 12^x = 144`

`=> 12^x = 12^2`

`=> x = 2`

Vậy, `x = 2`

________

`3^x - 5 = 81`

`3^x = 81 + 5`

`3^x = 86`

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`@` `\text {Kaizuu lv uuu}`

[ ( 6 . x - 39 ) : 7 ] . 4 = 12

[ ( 6 . x - 39 ) : 7 ] = 12 : 4

( 6 . x - 39 ) : 7 = 3

6 . x - 39 = 3 . 7

a) (x : 3 - 4) . 5 = 15

x : 3 - 4 = 15 : 5

x : 3 - 4 = 3

x : 3 = 3 + 4

x : 3 = 7

x = 7 . 3

x = 21.

6 . x - 39 = 21

6 . x = 21 + 39

6 . x = 60

x = 60 : 6

x = 10

Vậy x = 10

9.3x+1 = 81

= 81

[(6x-39):7].4=12                  (x:3-4).5=15                     9.3x+1=81

 (6x-39):7    =12:4=3            x:3-4    =15:5=3               27x+1=81

  6x-39         =3.7  =21          x:3       =3+4=7                    x+1=81:27=3

  6x              =21+39=60       x          =7.3=21                   x     =3-1=2

    x              =60:6   =10

Giúp mình với mình đang vội!!

cứ bình tĩnh bạn ơi

Úi khó thế em mới lớp 3

a) x=3

b) x=1

c) x=1 hoặc -5

d) x=2

e) x=2

g) x=2

h) x=1 hoặc x=0 hoặc x=-1

i) x=-1 hoặc x=0

\(a.4^x=64\)

\(4^x=4^3\)

\(\Rightarrow x=3\)

\(b,3^{x\times4}=81\)

\(3^{x\times4}=3^4\)

\(x\times4=4\)

\(\Rightarrow x=1\)

\(c,\left(2+x\right)^4=81\)

     \(\left(2+x\right)^4=3^4\) 

       \(2+x=3\)

                \(x=3-2\)

                \(x=1\)

\(d,5^{x\times5}=125\)

     \(5^{x\times5}=5^3\)

        \(x\times5=3\)

        \(x=3:5\)

        \(x=\frac{3}{5}\)

ban tu lam di,luoi the

bai ki vay ,

a, 4¹⁰. 2³⁰=2²⁰.2³⁰=2⁵⁰

b,9²⁵.27⁴.81³= 3⁵⁰.3¹².3¹²=3⁷⁴

Tương tự các câu khác....

a, 4¹⁰.2³⁰ = (2²)¹⁰.2³⁰ = 2²⁰.2³⁰ = 2⁵⁰
b, 9²⁵.27⁴.81³ = (3²)²⁵.(3³)⁴.(3⁴)³ = 3⁵⁰.3¹².3¹² = 3⁷⁴
c, 25⁵⁰.125⁵ = (5²)⁵⁰.(5³)⁵ = 5¹⁰⁰.5¹⁵ = 5¹¹⁵
d, 64³.4⁸.16⁴ = (2⁶)³.(2²)⁸.(2⁴)⁴ = 2¹⁸.2¹⁶.2¹⁶ = 2⁵⁰
e, 3⁸ : 3⁶ = 3²
2¹⁰ : 8³ = 2¹⁰ : (2³)³ = 2¹⁰ : 2⁹ = 2
12⁷ : 6⁷ = (12 : 6)⁷ = 2⁷
@Dương Tuyết Mai

Bài 1: 

a) \(33^{2x}:11^{2x}=81\)\(\Leftrightarrow\left(33:11\right)^{2x}=81\)

\(\Leftrightarrow3^{2x}=3^4\)\(\Leftrightarrow2x=4\)\(\Leftrightarrow x=2\)

Vậy \(x=2\)

b) \(\frac{x}{-5}=\frac{4}{21}\)\(\Leftrightarrow21x=-20\)\(\Leftrightarrow x=\frac{-20}{21}\)

Vậy \(x=\frac{-20}{21}\)

Bài 2:

\(A=\frac{1+3^4+3^8+3^{12}}{1+3^2+3^4+3^6+3^8+3^{10}+3^{12}+3^{14}}\)

\(=\frac{1+3^4+3^8+3^{12}}{\left(1+3^4+3^8+3^{12}\right)+\left(3^2+3^6+3^{10}+3^{14}\right)}\)

\(=\frac{1+3^4+3^8+3^{12}}{\left(1+3^4+3^8+3^{12}\right)+3^2.\left(1+3^4+3^8+3^{12}\right)}\)

\(=\frac{1+3^4+3^8+3^{12}}{\left(1+3^4+3^8+3^{12}\right).\left(1+3^2\right)}=\frac{1}{1+3^2}=\frac{1}{1+9}=\frac{1}{10}\)

\(33^{2x}:11^{2x}=81\)!

\(\left(33:11\right)^{2x}=81\)

\(3^{2x}=81\)

\(3^{2x}=3^4\)

\(2x=4\)

\(x=4:2\)

\(x=2\)

vậy \(x=2\)

\(\frac{x}{-5}=\frac{4}{21}\)

x.21=-5.4

x.21=-20

x=-20:21

\(x=-\frac{20}{21}\)

vậy \(x=-\frac{20}{21}\)