The slope-intercept equation is y=mx+b.
The slope formula is 
Our three points are (5,5), (-5,-7) and (0,-1)
Using our slope formula our slope becomes 
Then, if we use one of our points (pick whichever you want, although (0,1) is the easiest) to solve the equation. So,
. When we solve for x and y, we get -1=0+b, or b=-1.
When we plug that back into the equation, we get
.
Answer:
B.
Step-by-step explanation:
In this problem, it will be helpful to know the vertex form of a parabola, which is listed below:

is a constant which helps to determine whether the parabola opens up or down. If
, then the parabola opens downward and if
, the parabola opens upwards
is the vertex of the parabola
By looking at the graph, we can first see that the graph opens downwards, meaning that
. Thus, choices C and D are not valid. Now, let's use the vertex of the parabola to complete the equation.
The vertex of this parabola is (-1, 3), as shown by the graph. When we substitute this into our formula, we get:

The answer is a,
.