The circle passes through the point (-1,8). What is it’s radius? Options: A: 3 B: √8 C: √6 D: 2.75

B √8

Step-by-step explanation:

Equation of a circle is:

(x − h)² + (y − k)² = r²

where (h, k) is the center and r is the radius.

The center of the circle is (1, 6).

(x − 1)² + (y − 6)² = r²

The circle passes through the point (-1, 8).

(-1 − 1)² + (8 − 6)² = r²

4 + 4 = r²

r = √8

7.A (5,1)

B(5,7)

8. D (0,6)

Step-by-step explanation:

7.  One vertex is at (5,4)

Move 3 units either direction in x

(5-3,4) = (2,4)

(5+3,4) = (8,4)

Or move 3 units in the y direction

(5,4+3) = (5,7)

(5,4-3) = (5,1)

If x is less than 2 or greater than 8 it is too far from the one vertex we are given

If y is less than 1 or greater than 7 it is too far away from the one vertex we are given

C cannot be a vertex since y =9

D is not a vertex since the point is (2,6) and not (2,4) which we know is 3 units away

E is not a vertex since the point is (2,1) and not (2,4) which we know is 3 units away

8.  The center is (0,0)

The points have to add to a radius of 6

r^2 = 36

The sum of the x^2 and y^2 = 36

3^2 +0^2 = 9

4^2 +2^2 = 16+4 = 20

5^2 +3^2 = 25+9 = 34

0^2+6^2 =36  yes  for D

4^2 +4^2 =16+16 = 32

1^2+5^2 = 26