Question

Which is the equation of the circle graphed below?

A. (x+3)2 + (y + 4)2 = 5
B. ( x - 3)2 + (y + 4)2 = 5
C. (x + 3)2 + (y + 4)2 = 25
D. (x - 3)2 + (y + 4)2 = 25

Answer 1

The equation of a circle with center (a,b) and radius r is:

(x - a)^2 + ( y -b)^2 = r^2

The center of the circle graphed is (3,4).

And the radius may be calculated using the distance formula and the points (0,0) and (3,4)

r^2 = (3 - 0)^2 + (4 - 0)^2 = 9 + 16 = 25

=> (x - 3)^2 + (y - 4)^2 = 25

Which is likely the option D, but you made a mistake when wrote the numbers.

Answer: (x - 3)^2 + (y - 4)^2 = 25