2^x-14*2^(-x)+5=0
2^x-14*(1/2)^x+5=0
2^x-14*(1/2^x)+5=0
notez 2^x=a; a nr real, pozitiv
=> a-14*(1/a)+5=0
a-14/a+5=0
amplific cu a
a^2-14+5a=0
Δ=25-4*(-14)=25+56=81 => √Δ=9
a1= (-5-9)/2= -7 < 0
a2= (-5+9)/2= 2
revenind la notatie => 2=2^x <=> x=1 (solutie unica, reala)