Selections B and D both appear to be appropriate.
B) (x+8)² + (y+5)² = 13
D) (x+8)² + (y+5)² = 13
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The center is at the midpoint of the diameter, ((-10-6)/2, (-8-2)/2) = (-8, -5). For center (h, k) and radius r, the equation is
(x -h)² +(y -k)² = r²
(x -(-8))² +(y -(-5))² = (√13)²
(x+8)² + (y+5)² = 13
A because , well Y=4 and the points y coordinate is 4. And when a line is Y= a certain number, its a horizontal line parallel to x axis
a. The 
component tells you the particle's height:
b. The particle's velocity is obtained by differentiating its position function:
so that its velocity at time 
is
c. The tangent to 
at is
