If a pair of lines drawn through the origin forms an isosceles right-angled triangle with the line $2 x+3…

If a pair of lines drawn through the origin forms an isosceles right-angled triangle with the line $2 x+3 y=6$, then those lines are
  1. $x-5 y=0,5 x+y=0$
  2. $3 x-y=0, x+3 y=0$
  3. $5 x-y=0, x+5 y=0$
  4. $x-3 y=0,3 x+y=0$

Solution

Given line, $2 x+3 y=6$ Slope of line $=-2 / 3$ Equation of lines passing through origin and form an isosceles right angle triangle with the given line $\therefore$ Each angle be $45^{\circ}$. $\therefore$ Equation of line passing through origin and making an angle $45^{\circ}$ with the line $2 x+3 y=6$ is $\frac{y}{x}=\frac{-2 / 3 \pm \tan 45^{\circ}}{1 \mp\left(\frac{-2}{3}\right) \tan 45^{\circ}}$ $\Rightarrow \quad \frac{y}{x}=\frac{-2 / 3+1}{1+\frac{2}{3}}$ or $\frac{y}{x}=\frac{-2 / 3-1}{1-2 / 3}$ $\Rightarrow \quad \frac{y}{x}=\frac{1}{5}$ or $\frac{y}{x}=\frac{-5}{1}$ $\Rightarrow \quad 5 y=x$ or $y+5 x=0$ $\Rightarrow \quad x-5 y=0$ or $5 x+y=0$

Asked in: AP EAMCET 2021 (24 Aug Shift 2)

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