Question

Tìm x : 

2^x+3-2^x = 56
3^x+2-3^x+3=651

Answer 1

\(2^{x+3}-2^x=56\)

\(2^x.2^3-2^x=56\)

\(2^x\left(8-1\right)=56\)

\(2^x=2^3\)

\(x=3\)

Answer 2

\(2^{x+3}-2^x=56\\ \Rightarrow2^x\left(2^3-1\right)=56\\ \Rightarrow2^x=56:7=8=2^3\\ \Rightarrow x=3\\ 3^{x+2}-3^x+3=651\\ \Rightarrow3^x\left(3^2-1\right)=651-3=648\\ \Rightarrow3^x=648:8=81=3^4\\ \Rightarrow x=4\)