Question

Va rog frumos !!! Am nevoie ..

Answer 1

b₅ -b₂=78 <=> b₁·q⁴ -b₁·q=78 <=> b₁·q·(q³ -1)=78 <=> b₁·q·(q-1)·(q² +2q +1)=78 ;

S₃=13 <=> S₃=b₁· (q³- 1) /q-1 =13 <=> b₁· (q-1)·(q² +2q +1) /q-1 =13 (q≠1) <=> b₁·(q² +2g +1)=13 => q·(q-1)=6 iar q-1 <q <=> q·(q-1)=6=3·2 => q-1=2 => q=3 => b₁=1 de unde obtinem in final b₂=3 si b₅=81 .