Which of the following is the equation of a circle with a radius of 2.5 and its center at (-4, 3)?

A. (x - 4)^2 + (y + 3)^2 = 2.5
B. (x + 4)^2 + (y - 3)^2 = 2.5
C. (x - 4)^2 + (y + 3)^2 = 6.25
D. (x + 4)^2 + (y -3)^2 = 6.25

Respuesta :

The format for a circle is [tex](x-h) ^{2} +(y-k) ^{2} = r^{2} [/tex].  We are given our center of (-4, 3) where h is -4 and k is 3.  The radius of 2.5 will be squared to finish it off.  Filling in our h and k accordingly gives us [tex](x-(-4)) ^{2} +(y-3) ^{2} =6.25[/tex].  Clean that up a bit and we have [tex](x+4) ^{2} +(y-3) ^{2} =6.25[/tex], choice D above.
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