Answer:
a1 = 0.5; common ratio = 5
Step-by-step explanation:
Let the common ratio = r
a2 = 2.5
a3 = 2.5r
a4 = 2.5r * r = 2.5r^2
We are told a4 = 62.5, so
2.5r^2 = 62.5
Divide both sides by 2.5
r^2 = 25
r = 5
a2 = a1 * r
a1 = a2/r = 2.5/5 = 0.5
Answer: a1 = 0.5; common ratio = 5
