R= V/I
R is resistance 
V is voltage 
I is current 
We can multiply by I both side
I*R = (V/I)*I
I will cancel out from right side
so IR = V
we can write it 
V= IR 
V= RI + 0
 This equation is same as Y = MX +C
here Y is V
M is R which shows slope in a graph and it is constant 
C is Y intercept but it will be zero because if potential difference is zero then current will also be zero