Question

rezolvati ecuatia:$9^{x}$+2×$3^{x}$=99

Answer 1

[tex]Notam\ 3^x=t\\ (3^x)^2+2\cdot 3^x-99=0\\ t^2+2t-99=0\\ \triangle=2^2+4\cdot 99=400\\ t_{1/2}= \frac{-2\pm20}{2} \\ t_1= \frac{-2+20}{2}=9>0\\ t_2= \frac{-2-20}{2}=-11<0 \\ 3^x=9\\ 3^x=3^2\\ x=2[/tex]