Question

I have no idea how to do these problems:

Find an equation of each circle.
1. Center (3,5); tangent to the x axis
2. Center (5,-3); tangent to the y axis
3. Tangent to the x axis, y axis, and the line y=5 (two answers)

I just really need help understanding how to do this.

Answer 1

1. Did you sketch or just visualize the circle?
Isn't the radius 5 ?

so (x-3)^2 + (y-5)^2 = 25

2. Do it the same way.

3. y = 5 is a horizontal line 5 units above the x-axis.
I can visualize a circle in the first quadrant, and another in the second quadrant.
isn't the diameter 5 ?
so isn't the centre 2.5 up from the x-axis and 2.5 to the right of the y-axis?
mmmh?