Extra Circle Problems

Extra Circle Problems:

1) Find the equation(s) of the circle whose x-intercepts are (-4,0) and (2,0) and has a radius of 5.

Answer: (x + 1)2 + (y – 4)2 = 25 and (x + 1)2 + (y + 4)2 = 25

2) Find the equation(s) of the circle whose radius is 4 and is tangent to both the line y = x + 4 as well as the x-axis.

Answer: (x – 4√2)2 + (y – 4)2 = 16

3) Find the equation(s) of the circle whose diameter is 26, and which passes through (3, -5) and (3, 5). Notice these points are NOT the end points of a diameter.

Answer: (x – 15)2 + y2 = 169 and (x + 9)2 + y2 = 169

4) Find the equation(s) of the circle tangent to y = (2/3)x + 4 at the point (0, 4) and passes through the point (10, 2).

Answer: (x – 4)2 + (y + 2)2 = 52