1) fie [tex] 2^{x}=t,t\ \textgreater \ 0 \\ t^{2}-6t+8=0;t=2;t=4 [/tex]
revenim la substitutie si obtinem x=1 si x=2
2)fie[tex] ( \frac{1}{4} )^{x}=a,a\ \textgreater \ 0 \\ 4 a^{2}+15a-4=0;a=-4;a=- \frac{1}{4} [/tex]
deci ecuatia nu are solutii reale
3)[tex] 2^{x}= 3^{x};( \frac{2}{3})^x=1;x=0 [/tex]
4)[tex]3* 4^x+6^x-2*9^x=0 \\ impartim .la.4^x \\ 3+(\frac{3}{2})^x-2*( \frac{3}{2}) ^{2x}=0 \\ notam . (\frac{3}{2})^x=t \\ -2 t^{2}+t+3=0;t= \frac{3}{2} \\ revenind ;la;substitutie;x=1 [/tex]
