Respuesta :

nicolehopefaircloth

If a, b, c is an arithmetic sequence then a + c = 2b

a = 5, b = 9, c = 15

subtitute

a + c = 5 + 15 = 20

2b = 2 · 9 = 18

20 ≠ 18

Answer: The sequence 5, 9, 15 is not an arithmetic sequence.