Question

Câu 3 : 

a. x - 72 = 8

b. 2 . 3^x​ = 162

c. 3^x + 3^{x + 2} = 810

Answer 1

a)x- 72 =8

x= 8+72

x=80

b) 2.3^x=162

3x=162:2

3x=81

x=81:3

x=27

c)

3^x+3^x+2=810

=> 3^x.(1+3²)=810

=> 3^x.(1+9)=810

=> 3^x.10=810

=> 3^x=810:10

=> 3^x=81

=> 3^x=3⁴

=> x=4

Answer 2

a, X-72=8

<=>X=8+72

<=>X=80

b,2.3^x=162

<=>3^x=162:2

<=>3^x=81

<=>3^x=3⁴ =>X=4

c,3^x+3^x+2=810

<=>3^x.1+3^x.3²=810

<=>3^x(1+3²)=810

<=>3^x+10=810

<=>3^x=810:10=81

Mà 3⁴=81 hoặc (-3)⁴=81

 vậy x=4 hoặc x=-4 .