Answer:
Part 1) The radius is
Part 2) The points (-15,14) and (-15,-16) lies on the circle
Explanation:
step 1
Find the radius of the circle
we know that
The distance from the center to any point on the circumference is equal to the radius.
we have

Find the distance
the formula to calculate the distance between two points is equal to
substitute
step 2
The point (-15,y) lies on the circle
we know that
If a ordered pair lie on the circle, them the ordered pair must satisfy the equation of the circle
The equation of the circle is

The center is (-7,-1) an the radius is 17 units
substitute


substitute the x-coordinate of the point and solve for the y-coordinate
For x=-15





square root both sides




therefore
The points (-15,14) and (-15,-16) lies on the circle
see the attached figure to better understand the problem