Q41 / 90 · JEE Main 2022 (27 Jul Shift 2) · Mathematics

The equations of the sides AB,BC and CA of a triangle ABC are 2x+y=0, x+py=39 and x-y=3 respectively and P2,3 is its circumcentre. Then which of the following is NOT true

  • A
    AC2=9p
  • B
    AC2+p2=136
  • C
    32<area ∆ABC<36
  • Correct answer
    D
    34< area ∆ABC<38

Solution

FigureIntersection of 2x+y=0 & x-y=3 is A1,-2

Perpendicular bisector of AB is y-3=12x-2⇒x-2y+4=0

Take image of A along the perpendicular bisector of AB, we get 

x-11=y+2-2=-295=-185

i.e. x=-135, y=265

 B-135,265

This point lies on the line x+py=39

i.e. -135+p265=39⇒-1+2p=15

⇒p=8

Solving x+8y=39 and x-y=3, we get C7,4

Now AC2=1-72+-2-42=72=9p

and AC2+p2=72+64=136

Also ΔABC=121-21741-1352651

=1218+18×135

=9185=1625=32.4∉34,38

Hence, the correct answer is option: 'D'.

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