Standard form of circle is , where is center and  is the radius.

The circle center .

The circle is tangent to the -axis means the circle meets the -axis at only once.

All coordinates of at -axis are zero.

Since the center is , the point on the circle must be .

The distance between and is radius of the circle.

Radius of the circle is .

Substitute the values and in .

.

The circle equation in standard form is .