Question

What is the equation of the circle, with centre (-2,-7) and radius 3 units?
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Answer 1

(x + 2)² + (y + 7)² = 9

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) = (- 2, - 7) and r = 3, thus

(x - (- 2))² + (y - (- 7))² = 3², that is

(x + 2)² + (y + 7)² = 9

Answer 2

(x+2)^2 + (y+7)^2 = 9

Explanation:

The equation of a circle is given by

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

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

Substituting into this equation

(x--2)^2 + (y--7)^2 = 3^2

(x+2)^2 + (y+7)^2 = 3^2

(x+2)^2 + (y+7)^2 = 9