Question
If the equation x 2+ y 2 - 4x - 4y + 4 = 0 represents a circle, then its radius is
The correct answer is
2
Completing squares gives \((x-2)^2+(y-2)^2=4\). The radius is therefore \(\sqrt4=2\).
Was this answer helpful?
Important Questions from Equation of Circle
The equation x2 + y2 + 2gx + 2fy + c = 0 always represents a circle whose centre is (-g, -f) and radius is \(\sqrt {{g^2} + {f^2} - c} \). If g2 + f2 = c, then in this case, the circle is called as:
Find the equation of the circle which passes through (-1, 1) and (2, 1), and having centre on the line x + 2y + 3 = 0.
A circle is drawn on the chord of a circle x 2+ y 2= a 2as diameter. The chord lies on the line x + y = a. What is the equation of the circle?
- If the points lie on a circle, then what is/are the possible value(s) of k ?
- If a circle is drawn through A, B and D, then what is the diameter of the circle ?
Need Expert Advice?
