Direct variation describes a simple relationship between two variables . We say y varies directly with x
This means that as x increases, y increases and as x decreases, y decreases
Given equation is y = kx,
if x is doubled,
so plug in x = 2x in the given equation so new y1 will become
y1 = k ( 2x)
y1= 2kx
y1 = 2 y
So y becomes doubles