Question

Determine S9 of the series where a = 6 and r = 2. Provide a complete solution

Answer 1

if it is an arithmetic progression

`\displaystyle\bf \boxed{S_n=(a_1+a_n)/(2) \cdot n\quad; \quad a_n=a_1+(n-1)r}\\\\\\S_9=(6+6+16)/(2) \cdot9=126\\\\\\Answer: \boxed{S_9=126}` if it is a geometric progression
`\displaystyle\bf \boxed{ S_n=(a_1(1-r^n))/(1-r) \quad }\\\\\\S_9=(6(1-2^9))/(1-2) =511\cdot6=3066\\\\\\Answer:\boxed{ S_9=3066}`

Answer 2

Explanation:

my answer is in the image above