rezolvati in multimea numerelor reale ecuatia 3^x+3^x-1=4

Răspuns :


[tex] {3}^{x} + {3}^{x - 1} = 4 \\ {3}^{x} + \frac{ {3}^{x} }{3} = 4 \\ notam \: {3}^{x} = t > 0 \\ \\ t + \frac{t}{3} = 4 \\ 3t + t = 12 \\ 4t = 12 \\ t = 3 \\ \\ {3}^{x} = 3 \\ x = 1[/tex]
Fie 3^x = y
y +y/3 = 4
4y=12
y=3
3^x = 3
x=1.