Discussion Forum : Circles
Question -


The number of common tangents to the circles x2+y2+2x+8y23=0 and x2+y24x10y+19=0 is

Options:
A .   1
B .   2
C .   3
D .   4
Answer: Option C
:
C

To find the no. of common tangents, let's find the relation between distance between the centers of these circles and sum of their radii - 
Co-ordiantes of the center of first circle is (-1, - 4)
Co-ordiantes of the center of second circle is (2, 5)
thus the distance between them is -  (32+92)
=  3(10)
Now, the sum their radii will be - 
Radius of the first circle is -  2(10)
Radius of the second circle is - (10)
Sum of them will be -  3(10)
Since, the distance between the centres is equal to sum of their radii
Number of common tangents will be 3.



Was this answer helpful ?
Next Question
Submit Your Solution hear:

Your email address will not be published. Required fields are marked *