If a variable line drawn through the intersection of the lines x 3 + y 4 = 1 and x 4 + y 3 = 1 , meets the…

If a variable line drawn through the intersection of the lines x3+y4=1 and x4+y3=1 , meets the coordinate axes at A and B, A B,then the locus of the midpoint of AB is:
  1. 7xy=6x+y
  2. 4x+y2-28x+y+49=0
  3. 6xy=7x+y
  4. 14x+y2-97x+y+168=0

Solution

L1 :4x+3y-12=0

L2:3x+4y-12=0

L1+λL2=0

4x+3y-12+λ3x+4y-12=0

x4+3λ+y3+4λ-121+λ=0

Point A121+λ4+3λ, 0

Point B0,121+λ3+4λ

Mid point h=61+λ4+3λ .......i

k=61+λ3+4λ .......ii

Eliminate λ from equations i and ii then

6h+k= 7hk

Hence, locus is

6x+y= 7xy

Asked in: JEE Main 2016 (09 Apr Online)

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