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JEE Advanced 2019Paper 1
Exam
JEE Advanced
Year
2019
Paper
Paper 1
Subject
Mathematics
Chapter
Circle

JEE Advanced 2019 · Paper 1 · Mathematics · Circle

A line y = mx + 1 intersects the circle (x - 3) ^ 2 + (y + 2) ^ 2 =...

A line y=mx+1y = mx + 1 intersects the circle (x−3)2+(y+2)2=25{\left(x - 3\right)}^{2} + {\left(y + 2\right)}^{2} = 25 at the points PP and Q.Q . If the midpoint of the line segment PQPQ has x−x -coordinate −35,- \dfrac{3}{5}, then which one of the following options is correct?A line y = mx + 1 intersects the circle (x - 3) ^ 2 + (y + 2) ^ 2 = 25 at the points P and Q . If the midpoint of the

Options

  1. A6≤m<86 \le m < 8
  2. B2≤m<42 \le m < 4
  3. C4≤m<64 \le m < 6
  4. D−3≤m<−1- 3 \le m < - 1

Correct answer

B. 2≤m<42 \le m < 4

Step-by-step solution

A line y = mx + 1 intersects the circle (x - 3) ^ 2 + (y + 2) ^ 2 = 25 at the points P and Q . If the midpoint of the Equation of line PQ:y=mx+1PQ: y = mx + 1 Let RR be the mid point of PQPQ, so its xx-coordinate of midpoint =−35= - \dfrac{3}{5} Hence, coordinates of midpoint R(−35,−3m5+1)R\left(- \dfrac{3}{5}, - \dfrac{3m}{5} + 1\right) Let centre of circle is O(3,2)O\left(3, 2\right) Since, perpendicular dropped from centre upon any chord divides it in two equal parts. Hence, line PQPQ will be perpendicular to RORO ⇒mRQ⋅mRO=−1⇒ {m}_{RQ} ⋅ {m}_{RO} = - 1 ⇒m(−3m5+1+2−35−3)=−1⇒ m\left(\dfrac{- \dfrac{3m}{5} + 1 + 2}{- \dfrac{3}{5} - 3}\right) = - 1 ⇒m(−3m+15−18)=−1⇒ m\left(\dfrac{- 3m + 15}{- 18}\right) = - 1 ⇒m2−5m+6=0⇒ {m}^{2} - 5m + 6 = 0 ⇒m=2,3⇒ m = 2, 3

⇒2≤m<4⇒ 2 \le m < 4

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