Triangular numbers can be represented with equilateral triangles formed by dots. the first five triangular numbers are 1, 3, 6, 10 and 15. is there a direct variation between a triangular number and it’s position in the sequence? explain your reasoning

variation is y = kx  where y  would be the value of the number and x would be its position in the sequence, k is a constant 

so for consecutive values y/x would be a constant k 

In this case its not true becuse for example  3/1 = 3 and 6/3 = 2 

so there is no direct variation here.

I think Its D

Explanation: