Q90 / 160 · TS EAMCET 2021 (05 Aug Shift 1) · Mathematics

The line x3+y2=1 and a pair of lines both passing through origin forms an isosceles triangle. If this pair of lines are perpendicular, then the equation of the pair of straight lines is

  • A
    5x2-y2+24xy=0
  • Correct answer
    B
    5x2-y2-24xy=0
  • C
    5x2-y2+12xy=0
  • D
    5x2-y2-12xy=0

Solution

Pair of perpendicular lines passing through origin is

ax2+2hxy-ay2=0

or

x2+cxy-y2=0,

where c=2ha

Figure

tan45°=m--231+m-23=1

⇒3m+2=±3-2m

⇒m=-5,15

Pair of perpendicular are, y+5xy-x5=0

⇒x2-y2+-245xy=0, c=-245

⇒5x2-y2-24xy=0

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

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