Question

Rezolvat in multimea numerelor reale ecuatia: lg(x patrat+5)=lg9 helpppp :(

Answer 1

Cum avem ambii logaritmi in baza 10, egalam
x²+5=9
x²=9-5
x²=4
x= + / - 2

Answer 2

lg(x^2+5)=lg9
C.E.:x^2+5>0
=> (prin injectivitate) x^2+5=9=>x^2=4=>x1=2
x2=-2 nu verifica C.E.
x=2
S={2}