1) Find an equation with center on the line y =3x and tangent to y-axis with coordinates (0,2).

2) Find an equation for the tangent of a circle (x-3)^2 + (y+2)^2 = 13 on the points (0, -4).

3) Find an equation for the circle that passes through the points (0,0), (4,1), (3,-3).

I have no idea how to do these! Any hints would be helpful on how to start these problems :)

Thanks