# calc

posted by
**Melba**
.

standard equations of circles that have centers on line 5x-2y=-21 and are tangent to both axis.

Any ideas??

First express the line as in point slope form

y=(5/2)x - 21/2

The center must be on the line, so it is a point expressed as

(x,(5/2)x - 21/2)

In order for the circle to be tangent to both axis the center must be the same distance from both axis, so

x=y or x=(5/2)x - 21/2 solve for x

The standard equation for the circle is

(x-a)^2+(y-b)^2=r^2

You should be able to determine a,b and r.

After review, I don't know if I suggested how to find all the solutions.

You need to look at |x|=|y| or

|x|=|5/2)x - 21/2|

There should be one more solution to the question.

Thanks for all your help...