Question

Find S15 for the geometric series 72 + 12 + 2 + 1/3 +

Answer 1

Finish the equation. please and thank you

Answer 2

Hello,

$u_{1}=72\\ u_{2}=\dfrac{72}{6}\\ u_{3}=\dfrac{72}{6^{2}}\\ u_{15}=\dfrac{72}{6^{14}}\\ s=72*(1+\dfrac{1}{6^{1}}+\dfrac{1}{6^{2}}+\dfrac{1}{6^{3}}++...+\dfrac{1}{6^{14}})\\ =72*(\dfrac{\frac{1}{6^{15}}-1}{\frac{1}{6}-1}})\\ =72*(\dfrac{470184984576-1}{78364164095*5})\\ =86,400...$