Final answer:
The diameter of the circle represented by the equation (x+55)²+(y-11.5)²=121 is 22.
Step-by-step explanation:
The equation given ((x+55)²+(y-11.5)²=121) represents a circle in the xy-plane. The standard form of a circle's equation is (x-h)²+(y-k)²=r², where (h,k) is the center of the circle and r is the radius.
In this case, the number 121 is r², which means the radius (r) is the square root of 121, which is 11. The diameter of a circle is twice the radius, so the diameter of this circle is 2 * 11 = 22.