Question

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A circle is centered at the point (-7, -1) and passes through the point (8, 7).
The radius of the circle is
units. The point (-15,
) lies on this circle.
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Answer 1

The radius of the circle is:

sqrt[(8 - (-7))^2 + (7 - (-1))^2] = sqrt[15^2 + 8^2] = sqrt[225 + 64] = sqrt[289] = 17.

Therefore, the radius of the circle is 17 units.

The point (-15, -9) lies on this circle.

Answer 2

17 units.

Explanation:

To find the radius of the circle, we can use the distance formula between the center of the circle and a point on the circle.

Let's denote the center of the circle as (h, k) and the point on the circle as (x, y).

The distance formula is given by:

d = sqrt((x - h)^2 + (y - k)^2)

In this case, the center of the circle is (-7, -1) and a point on the circle is (8, 7).

Plugging these values into the distance formula:

d = sqrt((8 - (-7))^2 + (7 - (-1))^2)

= sqrt((8 + 7)^2 + (7 + 1)^2)

= sqrt(15^2 + 8^2)

= sqrt(225 + 64)

= sqrt(289)

= 17

Therefore, the radius of the circle is 17 units.

Now, to determine if the point (-15, y) lies on this circle, we can substitute the x-coordinate (-15) into the equation of the circle and solve for y.

Using the equation of a circle:

(x - h)^2 + (y - k)^2 = r^2

where (h, k) is the center of the circle and r is the radius, we have:

(-15 - (-7))^2 + (y - (-1))^2 = 17^2

(-15 + 7)^2 + (y + 1)^2 = 289

(-8)^2 + (y + 1)^2 = 289

64 + (y + 1)^2 = 289

(y + 1)^2 = 289 - 64

(y + 1)^2 = 225

y + 1 = ±√225

y + 1 = ±15

Solving for y, we have two possible values:

y + 1 = 15

y = 15 - 1

y = 14

y + 1 = -15

y = -15 - 1

y = -16

Therefore, the point (-15, 14) and (-15, -16) both lie on the circle with a radius of 17 units.