Помогите решить пример :с[latex]3^2^x^+^1-28*3^x+9=0[/latex]

[latex]3^{2x+1}-28*3^x+9=0\\3^{2x}*3-28*3^x+9=0\\3^x=t,t\ \textgreater \ 0\\3t^3-28t+9=0\\D=28^2-4*3*9=784-108=676=26^2\\\\t_1=\frac{28+26}{6}=\frac{54}6=9\\\\t_2=\frac{28-26}6=\frac{2}6=\frac{1}3\\\\ \left[\begin{array}{ccc}t=9\\t=\frac{1}3\end{array}\right=\ \textgreater \ \left[\begin{array}{ccc}3^x=3^2\\3^x=3^{-1}\end{array}\right=\ \textgreater \ \left[\begin{array}{ccc}x=2\\x=-1\end{array}\right[/latex]