Write the equation of the circle with a center at (-7,4) and a diameter of 18

A) (x + 7) 2 + (y - 4) 2 = 18

B) (x - 7) 2 + (y + 4) 2 = 324

C) (x + 7) 2 + (y - 4) 2 = 324

D) (x + 7) 2 + (y - 4) 2 = 81

E) (x - 7) 2 + (y + 4) 2 = 81

(x + 7) ^2 + (y - 4) ^2 = 81. This matches Answer Choice D.

Step-by-step explanation:

Apply the standard equation of a circle with center at (h, k) and radius r:

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

Here (h, k) is (-7, 4) and r is 18/2 or 9, and so the desired equation is

(x + 7) ^2 + (y - 4) ^2 = 81. This matches Answer Choice D.

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