1.
b₃=b₁·q²
1/2=b₁·(1/2)²
b₁=2
b₂=b₁q=1
S₃=b₁+b₂+b₃=2+1+(1/2)=3,5
2.
b₅=b₁·q⁴
-1/81=b₁·(-1/3)⁴
b₁=-1
b₂=b₁q=-1·(-1/3)=1/3
b₃=b₁·q²=1·(-1/3)²=1/9
S₃=b₁+b₂+b₃=1+(1/3)+(1/9)=13/9
1.
b₃=b₁·q²
1/2=b₁·(1/2)²
b₁=2
b₂=b₁q=1
S₃=b₁+b₂+b₃=2+1+(1/2)=3,5
2.
b₅=b₁·q⁴
-1/81=b₁·(-1/3)⁴
b₁=-1
b₂=b₁q=-1·(-1/3)=1/3
b₃=b₁·q²=1·(-1/3)²=1/9
S₃=b₁+b₂+b₃=1+(1/3)+(1/9)=13/9