Question

find the first four terms of the sequence given the rule:
$a_{n} = 4 \cdot (5)^{n - 1}$
20, 100, 500, 2500
5, 20, 80, 320
4, 20, 100, 500
4, 9, 14, 19

Explanation:

Step1: Calculate 1st term (n=1)

$a_1 = 4 \cdot (5)^{1-1} = 4 \cdot 5^0 = 4 \cdot 1 = 4$

Step2: Calculate 2nd term (n=2)

$a_2 = 4 \cdot (5)^{2-1} = 4 \cdot 5^1 = 4 \cdot 5 = 20$

Step3: Calculate 3rd term (n=3)

$a_3 = 4 \cdot (5)^{3-1} = 4 \cdot 5^2 = 4 \cdot 25 = 100$

Step4: Calculate 4th term (n=4)

$a_4 = 4 \cdot (5)^{4-1} = 4 \cdot 5^3 = 4 \cdot 125 = 500$

Answer:

4, 20, 100, 500