the line with the equation Y = 1 comes from the equation Y = ax + 1 it should be parallel to the xx axis
and that is why the slope is zero and finally it took the form Y = 1 because a=0
the line that is parallel to this line will have slope = 0 too and since passes from point -1,4 it takes the form
Y = ax+4 and since a=0 we have Y = 4 or Y-4=0 this is the equation we are looking for