Except don't write it as y = 

Instead write it as

y = x

That way, it is in the form y = mx + b, since it is the
same as

y = x + 0

But normally we don't write 0 terms.  But you want your x
to be to the right of the fraction , not in the
numerator with the 2 even though it is the same thing.
That's because it is not in the form mx until the x is 
written to the right of the m.

Edwin