The y-intercept is the point when the x-value is zero. If this graph is going by ones, it would be -1. In other words, the y-intercept is the dot that is on the y line.
Reason: So, on the Y-axis on the graph, only one point is actually touching that. That point is -1. Thus with thus information, we can assure that it's -1. I hope I didn't confuse you.
