Question

Tìm x biết

7^x+2+2.7^x—1=345

Ai làm nhanh mìn h tích đúng

Answer 1

7^x+2 + 2.7^x-1 = 345

=> 7^x-1+3 + 2.7^x-1 = 345

=> 7^x-1.7³ + 2.7^x-1 = 345

=> 7^x-1.343 + 2.7^x-1 = 345

=> 7^x-1.(343 + 2) = 345

=> 7^x-1.345 = 345

=> 7^x-1 = 1 = 7⁰

=> x - 1 = 0

=> x = 0 + 1 = 1

Vậy x = 1

Answer 2

7^{x + 2} + 2.7^{x - 1} = 345

=> 7^x . 7² + 2. 7^x : 7 = 345

=> 7^x.( 7² + 2 : 7) = 345

=> 7^x = 345 : 345/7

=> 7^x = 7

=> 7^x = 7¹

=> x = 1

Answer 3

\(7^{x+2}+2.7^{x-1}=345\)

=>\(7^{x-1}\left(7^3+2\right)=345\)

=>\(7^{x-1}.345=345\)

=>\(7^{x-1}=345:345\)

=>\(7^{x-1}=1\)

=>\(7^{x-1}=7^0\)

=>x-1=0

=>x=0+1

=>x=1

Vậy x=1

Answer 4

7^x+2+2.7^x-1=345

7^(x-1)+3+2.7^x-1=345

7^x-1.7³+2.7^x-1=345

7^x-1(7³+2)=345

7^x-1.345=345

7^x-1        =345:345

7^x-1       =1

7^x-1       = 7⁰

^x-1=0

^x=1