Question

Am nevoie de ajutor la exercițiile acestea. Mulțumesc anticipat.

Answer 1

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