Question

Tìm x biết
a)\(3^{x-1}=\frac{1}{243}\)

b)\(2^x+2^{x+3}=114\)

 

Answer 1

                                  

Answer 2

a) \(3^{x-1}=\frac{1}{243}\)

\(3^{x-1}=\left(\frac{1}{3}\right)^5\)

\(\Rightarrow3^{x-1}=3^{-5}\)

\(\Rightarrow x-1=-5\)

\(x=-4\)

b) \(2^x+2^{x+3}=114\)

\(2^x.\left(1+2^3\right)=114\)

\(2^x.9=114\)

\(2^x=\frac{38}{3}\)si đề

Answer 3

a) 3^x-1=1/243

   3^x-1=3^-5

   =>x-1=-5

      x=5+1=6

       Vậy x=6

b)câu này sai đề bạn ak.