\(4^x+5^x=9^x\Leftrightarrow\frac{4^x}{9^x}+\frac{5^x}{9^x}=1\Leftrightarrow\left(\frac{4}{9}\right)^x+\left(\frac{5}{9}\right)^x=1\)
\(+x=1:VT=\frac{4}{9}+\frac{5}{9}=1=VP,\text{ pt thỏa mãn.}\)
\(+x=0:\left(\frac{4}{9}\right)^0+\left(\frac{5}{9}\right)^0=2>1\Rightarrow pt\text{ vô nghiệm.}\)
\(+x>1:VT