Answer:
5ax + 5ay = 5a(x+y)
Step-by-step explanation:
95-55 is the simpliest form
First of all, I'm going to assume that we have a concave down parabola, because the stream of water is subjected to gravity.
If we need the vertex to be at
, the equation will contain a
term.
If we start with
we have a parabola, concave down, with vertex at
and a maximum of 0.
So, if we add 7, we will translate the function vertically up 7 units, so that the new maximum will be 
We have

Now we only have to fix the fact that this parabola doesn't land at
, because our parabola is too "narrow". We can work on that by multiplying the squared parenthesis by a certain coefficient: we want

such that:
Plugging these values gets us

As you can see in the attached figure, the parabola we get satisfies all the requests.
Use the slope formula
y2-y1
m=---------
x2-x1
(rise-->y over run-->x)
so it would be
9-5
m=-------
1-10
and that would simplify to
4
----
-9
and that would be your slope.
Hope that helped :-)
It is C, because the x values between the first dot and the second is 4. So you multiply the slope 4 times on the y value. The y value changes from -2 to -5, so -2 + 4*-3/4 should be equal to -5