[tex] 9^{x} - 10*3^{x-1} +1=0 \\ [/tex]
fie
[tex] 3^{x}=t,t\ \textgreater \ 0 \\ t^{2} -10*t* \frac{1}{3}+1=0 \\ 3 t^{2}-10t+3=0 [/tex]
Δ=100-36=64
[tex] t_{1}= \frac{10-8}{6}= \frac{1}{3} \\ t_{2}= \frac{10+8}{6}=3 [/tex]
revenim la substitutie si obtinem
[tex] 3^{x}= \frac{1}{3};x=-1 \\ 3^{x}=3;x=1 [/tex]
S={-1;1}
