Question

Next number 0,3,9,21,.....

Answer 1

Answer:

45

Step-by-step explanation:

0×2 +3 = 3

3×2 + 3= 9

9×2 + 3 = 21

21×2 + 3= 45

Answer 2

Answer:

$3(2^{i-1}-1)$

Step-by-step explanation:

Start the count on i = 1

$3(2^{1-1} - 1) = 3(2^{0} - 1) = 3 - 3 = 0\\3(2^{2-1} - 1) = 3(2^{1} - 1) = 6 - 3 = 3\\3(2^{3-1} - 1) = 3(2^{2} - 1) = 12 - 3 = 9\\....$