Find the differential equation of all the circles in the first quadrant which touch the coordinate axes.

Explanation

To find the differential equation of all circles in the first quadrant that touch the coordinate axes, we can follow these steps:

### Step 1: Understand the Circle's Equation
A circle that touches both the x-axis and y-axis in the first quadrant can be represented by the equation:
\[ (x - r)^2 + (y - r)^2 = r^2 \]
where \( r \) is the radius of the circle. The center of the circle is at the point \( (r, r) \).
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