B₁=Bn/q^(n-1)
Sn=B₁((q^n)-1))/(q-1)
1)
B₃=36, q=3, S₅=?
B₁=36/(3)²=4 S₅=(4*(3⁵-1)/2=484
2)B₄=64, q=-2, S₆=?
B₁=64/(-2)³=-8 S₆=[(-8)*((-2)⁶-1)]/-3=168
3)B₅=1 1/9, q=1/3, S₅=?
B₁=(11/9)/(1/3)⁴=99 S₅=[99*((1/3)⁵-1)]/(1/3-1)=147 8/9
4)B₄=121.5, q=-3, S₅=?
B₁=121.5/(-3)³=121.5/(-27)=-4.5 S₅=[(-4.5)*((-3)⁵-1)]/-4=274.5