SOLUTION: find a1 for the geometric sequence with the given terms a5=32 a7=128

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Question 1154845: find a1 for the geometric sequence with the given terms a5=32 a7=128
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!

a%28n%29+=+a%281%29%2A+r%5E%28n-1%29
a(5) = a(1)*r^4
a(7)= a(1)*r^6
32 = a(1)*r^4
128= a(1)*r^6
r^6/r^4 = 128/32
r^2 =4
r=+/-2
Plug r
in 32 = a(1)*r^4
32 = a( 1)*16
a1=2