Question

The equation of a circle is x2 + y2 + Cx + Dy + E = 0. If the radius of the circle is decreased without changing the coordinates of the center point, how are the coefficients C, D, and E affected? A. C, D, and E are unchanged. B. C increases, but D and E are unchanged. C. C and D decrease, but E is unchanged. D. C, D, and E increase. E. C and D are unchanged, but E increases.

Answer 1

answer E.

C and D are unchanged, but E increases.

Answer 2

C and D are unchanged, but E increases.

Explanation:

Given equation of circle

x^2+y^2+Cx+Dy+E=0

But we know that general equation of circle is with center at (h,k)

x^2 + y^2 -2hx -2ky + (h^2 + k^2 – r^2) = 0

Comparing both equations we get,

C = -2hx

D = -2ky

As in the given question we are not changing the coordinates of center so C and D will remain unchanged.

It also gives us

E = (h^2 + k^2 – r^2)

Decreasing r means that a lesser quantity will be subtracted from h^2 + k^2 which will increase the value of E.