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progresie geometrică a,a plus doi si a plus 8?

Răspuns :

Pg⇒b=√a×c
a=a
b=a+2
c=a+8
Pg=a+2=√a×(a+8)⇒(a+2)²=[√a×(a+8)]²⇒a²+4a+4=a×(a+8)⇒a²+4a+4=a²+8a⇒a²-a²+4a-8a+4=0⇒-4a=-4⇒a=-4/-4⇒a=1
succes