a) \(\frac{x^7}{81}=27\)

=> x⁷ = 27.81

=> x⁷ = 3³.3⁴

=> x⁷ = 3⁷

=> x = 3

Vậy x = 3

b) \(\frac{x^8}{9}=729\)

=> x⁸ = 729.9

=> x⁸ = 3⁶.3²

=> x⁸ = 3⁸ = (-3)⁸

=> \(x\in\left\{3;-3\right\}\)

Vậy \(x\in\left\{3;-3\right\}\)

x^7/81 = 27                                                    x^8/9 = 729

x^7 : 81= 27                                                   x^8  : 9 = 729

x^7       =27.81                                                x^8       = 729.9

x^7        =2187                                                x^8       =6561

x^7        = 3^7                                                  x^8       = 3^8

=> x      =3                                                       => x      = 3

\(\frac{x^7}{81}=27\Rightarrow x^7=27.81=2187\Rightarrow x=\sqrt[7]{2187}=3\)

\(\frac{x^8}{9}=729\Rightarrow x^8=729.9=6561\Rightarrow x=\sqrt[8]{6561}=3\)

\(\frac{x^7}{81}=27\)

\(\Rightarrow x^7.1=81.27\)

\(\Rightarrow x^7=2187\)

Ta thấy : \(3^7=2187\)

\(\Rightarrow x=\sqrt[7]{2187}=3\)

\(\frac{x^8}{9}=729\)

\(\Rightarrow x^8.1=729.9\)

\(\Rightarrow x^8=6561\)

\(\Rightarrow x=\sqrt[8]{6561}=3\)

\(\frac{x^7}{81}=27\Rightarrow x^7=27.81\Rightarrow x^7=3^3.3^4\Rightarrow x^7=3^7\Rightarrow x=3\)

\(\frac{x^8}{9}=729\Rightarrow x^8=729.9\Rightarrow x^8=3^6.3^2\Rightarrow x^8=3^8\Rightarrow x=3\)

a) Ta có: \(\frac{x^7}{81}=27\)

\(\Rightarrow x^7=27.81=2187\)

Mà \(2187=3^7\) \(\Rightarrow x^7=3^7\Leftrightarrow x=3\)

Vậy x = 3

b) Ta có: \(\frac{x^8}{9}=729\)

\(\Rightarrow x^8=729.9=6561\)

Mà \(6561=3^8\) \(\Rightarrow x^8=3^8\Leftrightarrow x=3\)

Vậy x = 3

CHÚC BẠN HỌC TỐT

\(\frac{x^7}{81}=27\Rightarrow27.81=x^7\Rightarrow x=3\)

\(\frac{x^8}{9}=729\Rightarrow x^8=729.9\Rightarrow x=3\)

tíc mình

nha

\(a.\)\(\frac{x^7}{81}=27\)

\(\Rightarrow x^7=27.81\)

\(\Leftrightarrow x^7=2187\)

\(\Leftrightarrow x^7=3^7\)

\(\Leftrightarrow x=3\)

\(b.\)\(\frac{x^8}{9}=729\)

\(\Rightarrow x^8=729.9\)

\(\Leftrightarrow x^8=6561\)

\(\Leftrightarrow x^8=3^8\)

\(\Leftrightarrow x=3\)

Vậy : Ở cả 2 câu x đều bằng 3 nhé.

~ Rất vui vì giúp đc bn ~

â)\(\dfrac{x^7}{81}=27\Leftrightarrow x^7=27\times81=2187\Leftrightarrow x=3\)

b)\(\dfrac{x^8}{9}=729\Leftrightarrow x^8=729\times9=6561\Leftrightarrow x=3\)

a, \(\dfrac{x^7}{81}=27\)=> x⁷=27. 81=>x⁷=2187=>x=3

b, \(\dfrac{x^8}{9}=729\)=>x⁸=729. 9= 6561=>x=3 hoặc -3

\(\dfrac{x^7}{81}=27\)

\(\Rightarrow x^7=2187\)

\(\Rightarrow x=3\)

\(\dfrac{x^8}{9}=729\)

\(\Rightarrow x^8=6561\)

\(\Rightarrow\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\)

a, không có x :v

b, (2x + 1)³ = 729

=> (2x + 1)³ = 9³

=> 2x + 1 = 9

=> 2x = 8

=> x = 4

vậy_

c, 9⁷ : x = 9⁷

=> x = 9⁷ : 9⁷

=> x = 1 

vậy_

d, x⁵ : 8³ = 64

=> x⁵ : 8³ = 8²

=> x⁵ = 8².8³

=> x⁵ = 8⁵

=> x = 8

vậy_

a) 3^x : 3 = 81

3^x = 27 = 3³

=> x = 3

b) (2x+1)³ = 729 = 9³

=> 2x + 1 = 9

2x = 8

x = 4

c) 9⁷: x = 9⁷

x = 1

d) x⁵ : 8³ = 64 = 8²

x⁵ = 8³.8² = 8⁵

=> x = 8

a, A= 5x4¹⁵ x 9⁹ - 4x3²⁰x 8⁹ = 5x2³⁰x3¹⁸-2²x 2²⁷x3²⁰

=2²⁹x3¹⁸(2x5-3²)=2²⁹x3¹⁸

B=5x2⁹x6¹⁹-7x2²⁹x27⁶=5x2⁹x2¹⁹x3¹⁹7x2²⁹x3¹⁸

=2³⁸x3¹⁸(5x3-7x2)=2²⁸-3¹⁸

^->A:B= 2²⁹x3¹⁸:2²⁸:3¹⁸=2

b sai nha

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