Question

Find the equation of a circle whose center is at (-3, 7) and radius is 9 units.

Answer 1

(x + 3)² + (y - 7)² = 81

Explanation:

the equation of a circle in standard form is

(x - h)² + (y - k)² = r²

where (h, k ) are the coordinates of the centre and r the radius

here (h, k ) = (- 3, 7 ) and r = 9 , then

(x - (- 3) )² + (y - 7)² = 9² , that is

(x + 3)² + (y - 7)² = 81

Answer 2

`x^2+y^2+6x-14y-23=0`

Explanation:

`(x-(-3))^2+(y-7)^2=9^2\\x^2+6x+9+y^2-14y+49=81\\x^2+y^2+6x-14y-23=0`