Question

find a1 for a geometric sequence if r=5 and a6=1000

Answer 1

\[a _{6}=ar^5\]

Answer 2

substitute the values to get a

Answer 3

im confused? in my class im working on geometric sequences and we have to use this formula an=a1(r)n-1

Answer 4

yes according to that formular substitute a6
ie
\[a _{6}=ar^{6-1}=ar^5\]

Answer 5

\[1000=a(5)^5\]
solve for a which is a1

Answer 6

id just think about inverting the sequence:

\[a_1=a_6\left(\frac 1r\right)^{6-1}\]

same results tho