Question

$3^{x} + 3^{-x} = \frac{10}3}$ cineva?:D

Answer 1

notam : 3^x=t, t>0
t+1/t-10/3=0m t^2-10t/3+1=0, delta=100/9-4= 64/9, x1=10/3+8/3/2=18/6=3, x2=10/3-8/3/2=2/6= 1/3.
revenim la notatie: 3^x=3, x=1, 3^x=3^-1, x=-1.
S={-1,1}.