If a point PP has coordinates (0,-2)(0,2) and QQ is any point on the circle, x^2+y^2 -5x-y+5=0x2+y25xy+5=0, then what is the maximum value of (PQ)^2(PQ)2?

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1 Answer
Mar 18, 2018

Answer is (2).

Explanation:

The center of the circle x^2+y^2-5x-y+5=0x2+y25xy+5=0 is (5/2,1/2)(52,12) and radius is sqrt((5/2)^2+(1/2)^2-5)=sqrt(3/2)=sqrt6/2(52)2+(12)25=32=62

Let us put the values of the corrdinates of P(0,-2)P(0,2) in the LHS of the equation of circle x^2+y^2-5x-y+5=0x2+y25xy+5=0 and we get

0+4-0+10+5=190+40+10+5=19 and as it is is greater than 00, the pint is outside the circle and maximum distance of PP from any pont on the circle would be,

distance of PP from centrer of circle plus radius.

Distance of P(0,-2)P(0,2) from center at (5/2,1/2)(52,12) is sqrt((5/2-0)^2+(1/2-(-2))^2)=sqrt(25/4+25/4)=sqrt(50/4)=(5sqrt2)/2(520)2+(12(2))2=254+254=504=522

and hence the maximum value of (PQ)^2(PQ)2 is

((5sqrt2)/2+sqrt6/2)^2(522+62)2

= (5sqrt2+sqrt6)^2/4(52+6)24

= (50+6+20sqrt3)/4=14+5sqrt350+6+2034=14+53

Hence answer is (2).

graph{(x^2+(y+2)^2-0.01)(x^2+y^2-5x-y+5)=0 [-3.917, 6.083, -2.48, 2.52]}