When a question is asking you for the y-intercept based on a graph, all you have to do is look to see at what point does the function cross/intersect the y-axis. The x-value will always be zero in a y-intercept. By looking at the graph you see that the function crosses the y-axis at the point (0, -1), which is your answer.
Answer: (0, -1)
It's a geometric sequence.

It's the sum for term 4 through term 15.
0.041 + 0.004
= 0.045
= 45/1000