Flag Analytical Geometry> If a point P has co-ordinates (0,-2) and ...
question mark

If a point P has co-ordinates (0,-2) and Q is any point on the circle, x2+ y2-5x-y+5=0, then the maximum value of (PQ)2 is:

Alex Wilson , 7 Years ago
Grade 12th pass
anser 3 Answers
Nitesh

Last Activity: 7 Years ago

P(0,-2) and Q on circle x²+y²-5x-y+5=0So centre of circle is (5/2 , 1/2)Which can directly find by trick ( general equation of circle is ax²+by²+2gx+2fy+c=0 so centre is (-g/2,-f/2))So farthest point is always perpendicular line so slope of line with point (5/2 , 1/2) and (0,-2) is -1 .So its perpendicular line slope is 1 .So equation of line which is farthest from circle is ( y-0)=1(x+2)= x-y+2 ans

Nitesh

Last Activity: 7 Years ago

P(0,-2) and Q on circle x²+y²-5x-y+5=0So centre of circle is (5/2 , 1/2)Which can directly find by trick ( general equation of circle is ax²+by²+2gx+2fy+c=0 so centre is (-g/2,-f/2) and radius is (g²+f²-c))So radius is (3/2)½ and total length from center to (0,-2) is. 5/(2)½. So distance PQ is (5 - (3)½)/ (2)½ and max value of (PQ)² is {14 - 5(3)½}.ans

Soumyadeep

Last Activity: 6 Years ago

as per the given equation of circle x^2+y^2-5x-y+5=O and the given point be P(0,-2);
we know that centre of the circle is (-g,-f) from general equation of circle
now on comparing both we get centre coordinate like (5/2,1/2); 
we know that radius of the circle is =√(g²+f²-c) from general equation
therefore radius of this circle is (3½/2½)
distance of the point P from centre is (5/2½)
Now For PQ to be maximum the distance should be equal = the radius + the distance of the point from centre)
PQ =(5+3½)/2½
PQ²=14+5√3

Provide a better Answer & Earn Cool Goodies

Enter text here...
star
LIVE ONLINE CLASSES

Prepraring for the competition made easy just by live online class.

tv

Full Live Access

material

Study Material

removal

Live Doubts Solving

assignment

Daily Class Assignments


Ask a Doubt

Get your questions answered by the expert for free

Enter text here...