Question

if t8=640,r=2,find a

Answer 1

I think you question is incomplete.....

Answer 2

Answer:

a=5

Step-by-step explanation:

t8=640 ;  r=2

t8=ar^7

bcoz, tn=ar^n-1

640=a 2^7

a=640/218

therefore,

a=5..........