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QJEEM22Ma9654: JEE Main 2022 Mathematics - Class 11 JEEM22Ma9654 Solution: A particle is moving in the xy-plane along a curve C passing…

A particle is moving in the xy-plane along a curve C passing through the point (3, 3). The tangent to the curve C at the point P meets the x-axis at Q. If the y-axis bisects the segment PQ, then C is a parabola with :

Multiple Choice Options

  • A length of latus rectum 3
  • B length of latus rectum 6
  • C focus (43,0)\left( {{4 \over 3},0} \right)
  • D focus (0,34)\left( {0,{3 \over 4}} \right)

Step-by-Step Verified Solution

According to the question (Let P(x, y))

2x−ydxdy=02x - y{{dx} \over {dy}} = 0

( ∵\because equation of tangent at P:y−y=dydx(y−x)P:y - y = {{dy} \over {dx}}(y - x) )

∴\therefore 2dyy=dxx2{{dy} \over {y}} = {{dx} \over x}

⇒2ln⁡y=ln⁡x+ln⁡c\Rightarrow 2\ln y = \ln x + \ln c

⇒y2=cx\Rightarrow {y^2} = cx

∵\because this curve passes through (3, 3)

∴\therefore c = 3

∴\therefore required parabola y2=3x{y^2} = 3x and L.R = 3

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