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

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

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

5^x+1 - 5^x = 100

5^x. 5 - 5^x . 1 = 100

5^x . ( 5 - 1 ) = 100

5^x . 4 = 100

5^x =100 : 4

5^x = 25

5^x= 5²

=> x = 2

2)

9^2x : 9 = 729

9^2x : 9¹ = 729

9^2x-1 = 729

9^2x-1 = 9³

=> 2x - 1 = 3

2x = 3 + 1

2x = 4

=> x = 4 : 2

x = 2

MÌNH LÀM CÂU 2 THÔI NHÉ

                                  9^2X:9=729

                                     9^2X=729:9

                                      9^2X=81

                                       9^2X=9²

              SUY RA;         2.X=2

                                       X=2:2

                                       X=1

Vậy x=1

Cẳm ơn

8317161

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

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

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

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

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

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

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

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

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

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