b. 9 × ( x + 5) = 729

x + 5 = 729 : 9

x + 5 = 81

x = 81 - 5

x = 76

b. 9 × ( x + 5 ) = 729

x + 5 = 729 : 9

x + 5 = 81

x = 81 – 5

x =76

a) (9458-x)x5=41195                                              b) (9x x)x6=23490 

    9458-x   =41195:5                                                    9 x x     =23490:6 

    9458-x   =8239                                                         9 x x      =3916

             x=9458-8239                                                      x          = 3915:9

             x=1219                                                               x=435

c)9x(x+5)=729

        x+5=729:9

        x+5=81

            x=81-5

            x=76       k mk nha

a) (9458 - X) x 5 = 41195

     9458 - X = 41195 : 5

     9458 - X = 8239

                X = 9458 - 8239

                X = 1219

b) (9 x X) x 6 = 23490

     9 x X = 23490 : 6

     9 x X = 3915

           X = 3915 : 9

           X = 435

c) 9 x (X + 5) = 729

           X + 5 = 729 : 9

           X + 5 = 81

           X = 81 - 5

           X = 76

a, x-13=184:8

x-13=23

x=23+13

x=36

Vậy x=36

b,x:7=833:7

x:7=119

x=119x7

x=833

Vậy x=833

c, x+5=729:9

x+5=81

x=81-5

x=76

Vậy x=76

d,50-(17-x)=36

17-x=50-36

17-x=14

x=17-14

x=3

Vậy x=3

Hok tốt

Trả lời :

a, Check lại đề.

b, 9^{x - 4} = 729

=> 9^{x - 4} = 9³

=> x - 4 = 3

=> x = 7

Vậy x = 7.

phần a mik ghi thiếu,là 625 nha cậu

a) (2^x)⁵ : 4³ = 8¹⁵ => 2^5x = 8¹⁵.4³ = (2³)¹⁵.(2²)³ = 2⁴⁵.2⁶ = 2⁵¹ => 5x = 51 => x = 10,2 

b) (3²)^x .9³ = 243⁹ => 3^2x = 243⁹ : 9³ = (3⁵)⁹ : (3²)³ = 3⁴⁵ : 3⁶ = 3³⁹ => 2x = 39 => x = 19,5

c) (1/125)³.5^x = 25⁵ => 5^x = 25⁵ : (1/125)³ = (5²)⁵ : (1/5³)³ = 5¹⁰ : (5^-3)³ = 5¹⁰ : 5^-9 = 5¹⁹ => x = 19

d) 1/81 : 3^x = 1/729 => 3^x = 1/81 : 1/729 = 1/3⁴.729 = 3^-4.3⁶ = 3² => x = 2

e) (5x - 2)⁴ = 16⁸ = (16²)⁴ = 256⁴

=> 5x - 2 = -256 ; 256 => 5x = -254 ; 258 => x = -50,8 ; 51,6

P/S : Thay x = 10,2 vào câu a , x = 19,5 vào câu b sẽ thấy điều hư cấu : 2^10,2 và 9^19,5.Ko thể tính được giá trị của 2 lũy thừa này.

692157

`Answer:`

\(\left(x+\frac{1}{3}\right)+\left(x+\frac{1}{9}\right)+\left(x+\frac{1}{27}\right)+...+\left(x+\frac{1}{729}\right)=\frac{4209}{729}\)

\(\Leftrightarrow\left(x+\frac{1}{3}\right)+\left(x+\frac{1}{3^2}\right)+\left(x+\frac{1}{3^3}\right)+...+\left(x+\frac{1}{3^6}\right)=\frac{4209}{729}\)

\(\Leftrightarrow6x+\left(\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^6}\right)=\frac{4209}{729}\text{(*)}\)

Đặt \(N=\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^6}\)

\(\Leftrightarrow3N=1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^5}\)

\(\Leftrightarrow3N-N=\left(1+\frac{1}{3}+\frac{1}{3^2}+..+\frac{1}{3^5}\right)-\left(\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^6}\right)\)

\(\Leftrightarrow2N=1-\frac{1}{3^6}\)

\(\Leftrightarrow2N=\frac{728}{729}\)

\(\Leftrightarrow N=\frac{364}{729}\)

\(\text{(*)}\Leftrightarrow6x+\frac{364}{729}=\frac{4209}{729}\)

\(\Leftrightarrow6x=\frac{3845}{729}\)

\(\Leftrightarrow x=\frac{3845}{4374}\)

a)x*5³=5⁵

=>x*125=3125

=>x=3125:125

=>x=25

b) (x+1)*3⁴=3⁶

=>(x+1)*81=729

=>x+1=729:81

=>x+1=9

=>x=9-1

=>x=8

c) 9^x-1=729

Mà:9³=729

=> 9^x-1=9³

=>x-1=3

=>x=3+1

=>x=4

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 \(x\in\left\{3;-3\right\}\)