Question

Cho \(9^x+9^{-x}=14\) Tính

\(P=\dfrac{6+3\left(3^x+3^{-x}\right)}{2-3^{x+1}-3^{1-x}}\)

 

Answer 1

\(\left(3^x+3^{-x}\right)^2=9^x+9^{-x}+2.3^{x-x}=14+2=16\)

\(\Rightarrow3^x+3^{-x}=4\)

\(P=\dfrac{6+3\left(3^x+3^{-x}\right)}{2-3\left(3^x+3^{-x}\right)}=\dfrac{6+3.4}{2-3.4}=...\)