Question

If $g ^ { 2 } + f ^ { 2 } = c$, then the equation$x ^ { 2 } + y ^ { 2 } + 2 g x + 2 f y + c = 0$will represent.

• A. A circle of radius g
• B. A circle of radius f
• C. A circle of diameter$\sqrt { c }$
• D. A circle of radius 0

Answer 1

Answer: (D)

A circle of radius 0

Answer 2

Radius of given circle $= \sqrt { g ^ { 2 } + f ^ { 2 } - c }$

$g ^ { 2 } + f ^ { 2 } = c$ (given) , $\therefore$ Radius = 0.