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Sn=a₁×(1-q do n)/(1-q)
an=a₁×q do potegi (n-1)
1]
a1=2
q=3
Sn2(1-3 do n)/(1-3)
242=2(1-3 do n)/-2
-242=1-3 do n
3 do n=243
3 do n=3⁵
n=5
........
an=2×3 do (n-1)
a₅=2q⁴=2×3⁴=162
2]
a₇=a₁q⁶
-½=a₁(½)⁶
-½=1/64a₁
a₁=-8
...........
S₇=-8[1-(½)⁷]/(1-½)=-16×127/128=-15,875
3]
1023=a₁(1-2¹⁰)/(1-2)
-1023=-1023a₁
a₁=1
a₁₀=a₁q⁹=1×2⁹=512
4]
a₇=a₁q⁶
625=1/25q⁶
q⁶=15625
q=5 lub q=-5
S₇=1/25(1-5⁷)/(1-5)=781,24 lub
S₇=1/25(1-(-5)⁷]/(1+5)=520,84
5]
a₈=a₁q⁷=√8×(-√2)⁷=-6√2
S₈=√8(1-(-√2)⁸]/(1+√2)=√8×[-15(1-√2)/(1-2)=√8-15√16=2√2-60=2(√2-30)