Question 771636
Here is some help for "touch both axes".  
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To be simpler, choose a circle in quadrant 1.  To touch both axes, the center point is the radius value distance from both number lines.  If the center of the circle is r, then this means the center (h, k) would be (r, r).  The related standard form equation would then use those values (or variables, in this generalization) to give  {{{(x-r)^2+(y-r)^2=r^2}}}.  


This picture shows C at the center point, (r, r):

{{{drawing( 300, 300, 
          0, 10,
          0, 10,
          red( circle( 5, 5, 3 ) ),
          locate( 5, 5, C_r_r ),
line(2,2,2,8),
line(2,2,8,2),
locate(1.8,5,r),
locate(5,1.8,r)
 )}}}