Question

a is a number such that the sequence given below is an arithmetic progression.

' 0, a, 2a, 21, ...' then a stands for the number .

Answer 1

Step-by-step explanation:

If a, b, c . are in AP. then,

common difference,

d = b-a = c-b => b = (a+c) /2

$2a \: = (21 + a) \div 2 \\ = > 4a = 21 + a \\ = > 3a = 21 \\ = > a = 7$