Question:
<p>If the circle x<sup>2</sup> + y<sup>2</sup> + 4x + 22y + c = 0 bisects the circumference of the circle x<sup>2</sup> + y<sup>2</sup> - 2x + 8y - d = 0 (c, d > 0), then maximum value of cd is :</p>
<p style="display:inline">625</p>
<p style="display:inline">25</p>
<p style="display:inline">425</p>
<p style="display:inline">125</p>
Step-by-Step Solution
Key Concept: When a circle bisects the circumference of another, their common chord must pass through the center of the circle being bisected.
<p>625</p>
Correct Answer: A