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QJEEM25Maef1e: JEE Main 2025 Mathematics - Class 11 JEEM25Maef1e Solution: Two parabolas have the same focus (4, 3) and their directrices…

Two parabolas have the same focus (4, 3) and their directrices are the x-axis and the y-axis, respectively. If these parabolas intersect at the points A and B, then (AB)2 is equal to :

Multiple Choice Options

  • A 384
  • B 392
  • C 96
  • D 192

Step-by-Step Verified Solution

JEE Main 2025 (Online) 29th January Morning Shift Mathematics - Parabola Question 10 English Explanation

Let intersection points of these two parabolas are A(x1,y1)& B(x2,y2)\mathrm{A}\left(\mathrm{x}_1, \mathrm{y}_1\right) \& \mathrm{~B}\left(\mathrm{x}_2, \mathrm{y}_2\right)

∵\because equation of parabola I and II are given below

amp;∴(x−4)2+(y−3)2=x2..... (1)amp;&(x−4)2+(y−3)2=y2..... (2)\begin{aligned}& \therefore(\mathrm{x}-4)^2+(\mathrm{y}-3)^2=\mathrm{x}^2 \quad\text{..... (1)}\\& \&(\mathrm{x}-4)^2+(\mathrm{y}-3)^2=\mathrm{y}^2 \quad\text{..... (2)}\end{aligned}

Here A(x1,y1)&B(x2,y2)A\left(x_1, y_1\right) \& B\left(x_2, y_2\right) will satisfy the equation

Also from equations (1) & (2), we get x=yx=y .......(3)

Put x=yx=y in equation (1)

We get x2−14x+25=0x^2-14 x+25=0

amp;x1+x2=14amp;x1x2=25amp;∴AB2=(x1−x2)2+(y1−y2)2amp;=2(x1−x2)2amp;=2[(x1+x2)2−4x1x2]amp;=192\begin{aligned}& x_1+x_2=14 \\& x_1 x_2=25 \\& \therefore A B^2=\left(x_1-x_2\right)^2+\left(y_1-y_2\right)^2 \\& =2\left(x_1-x_2\right)^2 \\& =2\left[\left(x_1+x_2\right)^2-4 x_1 x_2\right] \\& =192\end{aligned}

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