I'm not an expert, but from what I remember, the y-intercept is where the line passes the y-axis, so in this case, it would be 4. In order to get to the next point, you would have to go down 4 points and left 2, which would be 4/2 = 2/1 = 2. Take my answer with a grain of salt, but I think it would be y = 2x + 4. There doesn't seem to be a graph with squares, so I can't be absolutely certain.
