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S_n=\frac{a_1(1-q^n)}{1-q} a) q=\frac{1}{8}:\frac{1}{16}=2 S_8=\frac{\frac{1}{16}(1-2^8)}{1-2} S_8=\frac{\frac{1}{16}(1-256)}{-1} S_8=\frac{\frac{1}{16}(-255)}{-1} S_8=\frac{\frac{-255}{16}}{-1} S_8=\frac{255}{16} b) q=6:18=\frac{1}{3} S_8=\frac{18(1-(\frac{1}{3})^8)}{1-\frac{1}{3}} S_8=\frac{18(1-\frac{1}{6561})}{\frac{2}{3}} S_8=\frac{18\cdot \frac{6560}{6561}}{\frac{2}{3}} S_8=27\cdot \frac{6560}{6561} S_8=\frac{6560}{243} c) q=-30:15=-2 S_8=\frac{15(1-(-2)^8)}{1+2} S_8=\frac{15(1-256)}{3} S_8=\frac{15(-255)}{3} S_8=5\cdot (-255) S_8=-1275 d) q=-7:(-7)=1 Da q=1 wzór na sumę jest postaci: S_n=n\cdot a_1 S_8=8\cdot (-7) S_8=-56