The general form of the equation that represents a direct variation between y and x is as follows:
Where k is the proportion constant
We will check the given equation:
a) y = 4x + 1
The equation doesn't have the general form
so, the answer is NO
b) y = 7.5x
It is like the general form and k = 7.5
so, the answer is Yes
c) y = (1/15)x
it is like the general form and k = 1/15
so, the answer is Yes
d) y = 6/x
It is not like the general form
So, the answer is No