Question

How can you show that two objects are proportional with an equation

Answer 1

For an equation to be proportional, it must have no y intercept, and it must have a slope. So, 
y=4x+4  This equation isn't proportional because it has a y-intercept (+4)
y=4x+2  This equation isn't proportional because it has a y-intercept (+2)
y=4x      This equation is proportional because it has no y-intercept, and a                     slope.