\(3^x+4^x=5^x\\ \Leftrightarrow\left(\dfrac{3}{5}\right)^x+\left(\dfrac{4}{5}\right)^x=1\)
TH 1 : x<2 \(\Rightarrow\left(\dfrac{3}{5}\right)^x+\left(\dfrac{4}{5}\right)^x>\left(\dfrac{3}{5}\right)^2+\left(\dfrac{4}{5}\right)^2=1\)
TH2 : x=2 thỏa
TH3 : x>2
\(\Rightarrow\left(\dfrac{3}{5}\right)^x+\left(\dfrac{4}{5}\right)^x< \left(\dfrac{3}{5}\right)^2+\left(\dfrac{4}{5}\right)^2=1\)