The diameter of the equation of a circle in the xy-plane as shown is 26 units.
The standard form for finding the equation of a circle is expressed as:

For us to get the diameter of the circle, we need to get the radius of the circle first calculated as shown:

Given the equation of the circle expressed as 
Compare with the general formula:
2gx = -6x
g = -6/2
g = -3
Similarly;
2fy = 8y
2f = 8
f = 4
C = -144
Substitute into the formula for calculating the radius;

Get the diameter of the circle
d = 2r
d = 2(13)
d = 26 units
Hence the diameter of the equation of a circle in the xy-plane as shown is 26 units.
Learn more here: brainly.com/question/12908710