Question

tìm x, biết:

a, 27^x : 81^2=9

b, 125/25^x=5

c, 1/9. 27^x=3^x

d, 3^4-x=27

 

Answer 1

a: \(\Leftrightarrow3^{3x}:3^8=3^2\)

=>3x-8=2

=>3x=10

hay x=10/3

b: \(\Leftrightarrow25^x=25\)

hay x=1

c: \(\Leftrightarrow9^x=\dfrac{1}{9}\)

hay x=-1

d: =>4-x=3

=>x=1

Answer 2

a) 27^x : 81² = 9

=> 3x - 8 = 2 

=> 3x = 10

hay x = 10/3 

vậy x = [10 ; 10/3]

b) 125/25^x = 5

=> 25^x = 25

=> hay x = 1

vậy x = [25 ; 1]

c) 1/9 . 27^x = 3^x

=> 9^x = 1/9

=>  hay x = - 1

vậy x = [1/9 ; - 1]

d) 3⁴ - x = 27

   27 - x = 27

         x = 27 - 27 

         x = 0