# Analytic Geometry

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What are the equations of the circles tangent to the x-axis, of radius 4 and whose center is at (-2,y)

• Analytic Geometry -

Since (-2,0) must be on the circle , (it is tangent to that point)
y must be either 4 or -4

first case: y = 4
centre is (-2,4) radius is 4

equation: (x+2)^2 + (y-4)^2 = 16

you try the other circle with centre (-2,-4)

• Analytic Geometry -

-2,-4

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