Remember that
A relation between two variables x and y is a function, if for one value of x there are only one value of y
In this problem
for one value of x there are one value of y
therefore
Is a function
we know that
A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form
y=kx
where
k is the constant of proportionality
k=y/x
Find the value of k
For x=2, y=4
k=6/2=2
For x=3, y=6
k=6/3=2
For x=-2, y=-4
k=-4/-2=2
The value of k is the same, that means, Its a proportional relationship
the linear equation is
y=2x