Mark the correct alternatives in each of the following :
The equation x2 + y2 + 2x – 4y + 5 = 0 represents
Given equation is:
⇒ x2 + y2 + 2x - 4y + 5 = 0
We know that for a pair of straight lines ax2 + 2hxy + by2 + 2gx + 2fy + c = 0, the conditions to be satisfied is abc + 2fgh - af2 - bg2 - cf2 = 0, h2≥ab, g2≥ca and f2≥bc.
Here we can see that h = 0 a = b = 1
⇒ h2 = 02 = 0
⇒ ab = 1.1 = 1
⇒ h2≤ab. So, the equation doesn’t represent a pair of straight lines.
⇒ x2 + y2 + 2x - 4y + 5 = 0
⇒ (x2 + 2x + 1) + (y2 - 4y + 4) = 0
⇒ (x + 1)2 + (y - 2)2 = 0
The equation represents circle with zero radius. This is a point circle.
∴The correct option is (a).