Question

If the coordinate of one end of a diameter of the circle $x^2+y^2+4x-8y+5=0$ is $(2,1)$, the coordinates of the other end is

• A. $(-6,-7)$
• B. $(6,7)$
• C. $(-6,7)$
• D. $(7,-6)$

Answer 1

The correct option is C $(-6,7)$

Since, one end of a diameter of the circle is $(2,1)$
Let the other end of a circle is $(h,k)$
But centre of a circle is $(-2,4)$
$\therefore$ $\frac{h+2}{2}=-2,\frac{k+1}{2}=4$
$\Rightarrow$ $h=-6$ and $k=7$
Hence, required points is $(-6,7)$