A single A.M between a and b is

(a+b)/2

(a-b)/2

2ab/(a+b)

None of these

Let, a and b two given numbers.

Let,

$A_{1}, A_{2}, A_{3} . . . . . . . . . . . . . A_{n}$ be Arithmetic means between a and b.

$a, A_{1}, A_{2}, A_{3} . . . . . . . . . . . . . A_{n},$