the y intercept is the value of y when x=0, it is represented by the letter b in y=mx+b
#1: b=0
#2: b=4, when x=0, y=4
#3: you have to work out b in this one by first writing the equation in point-slope form: y+4=2(x-1), when x=0, y=-6, so b=-6
#4: from the graph you can see the line cross the y axis at (0,5), so b=5
#4 has the largest y intercept.
