Respuesta :
A direct variation means proportionality. Triangular numbers are quadratic in n. T(n)=n(n+1)/2. So no.
direct 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.