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QJEEAdv08Ma244f: JEE Advanced 2008 Mathematics - Class 11 JEEAdv08Ma244f Solution: Consider where p is a real number, and STATEMENT-1 : If line is …

Consider

 L1:  2x  +  3y + p  −  3=0\,{L_1}:\,\,2x\,\, + \,\,3y\, + \,p\,\, - \,\,3 = 0

 L2:  2x  +  3y + p  +  3=0\,{L_2}:\,\,2x\,\, + \,\,3y\, + \,p\,\, + \,\,3 = 0

where p is a real number, and  C: x2 + y2 + 6x −10y + 30=0\,C:\,{x^2}\, + \,{y^2}\, + \,6x\, - 10y\, + \,30 = 0

STATEMENT-1 : If line L1{L_1} is a chord of circle C, then line L2{L_2} is not always a diameter of circle C
and

STATEMENT-2 : If line L1{L_1} is a diameter of circle C, then line L2{L_2} is not a chord of circle C.

Multiple Choice Options

  • A Statement-1 is True, Statement-2 is True; Statement-2 is a correct rexplanation for Statement-1
  • B Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct rexplanation for Statement-1
  • C Statement-1 is True, Statement-2 is False
  • D Statement-1 is False, Statement-2 is True

Step-by-Step Verified Solution

Equation of circle C is

(x+3)2+(y−5)2=9+25−30=4{(x + 3)^2} + {(y - 5)^2} = 9 + 25 - 30 = 4

⇒(x+3)2+(y−5)2=22\Rightarrow {(x + 3)^2} + {(y - 5)^2} = {2^2}

Centre = (3, −- 5)

If L1 is diameter, then it passes through the center (3, −- 5),

∴\therefore 2(3)+3(−5)+p−3=0⇒p=122(3) + 3( - 5) + p - 3 = 0 \Rightarrow p = 12

∴\therefore L1 is 2x+3y+9=02x + 3y + 9 = 0

and L2 is 2x+3y+15=02x + 3y + 15 = 0

Distance of centre of circle from {L_2}(d) = \left| {{{2(3) + 3( - 5) + 15} \over {\sqrt {{2^2} + {3^2}} }}} \right| = {6 \over {\sqrt {12} }} < 2 [radius of circle]

∴\therefore L2 is a chord of circle C.

Statement 2 is false.


IIT-JEE 2008 Paper 2 Offline Mathematics - Circle Question 16 English Explanation

Statement - 1 is true. If L1 is a chord, L2 may lie outside the circle.

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