The Cartesian equation of the line passing through the point $(-1,3,-2)$ and perpendicular to the lines…

The Cartesian equation of the line passing through the point $(-1,3,-2)$ and perpendicular to the lines $\frac{x}{1}=\frac{y}{2}=\frac{z}{3}$ and $\frac{x+2}{-3}=\frac{y-1}{2}=\frac{z+1}{5}$ is
  1. $\frac{x-1}{2}=\frac{y+3}{7}=\frac{z-2}{4}$
  2. $\frac{x-1}{-2}=\frac{y+3}{-7}=\frac{z-2}{-4}$
  3. $\frac{x+1}{2}=\frac{y+3}{7}=\frac{z+2}{4}$
  4. $\frac{x+1}{2}=\frac{y-3}{-7}=\frac{z+2}{4}$

Solution

$P=(-1,3,-2)$ Let $\mathrm{dr}$ 's or required line be $(a, b, c)$ Dr's of line $\frac{x}{1}=\frac{y}{2}=\frac{z}{3}$ are $(1,2,3)$ Given that required line perpendicular to above line $\Rightarrow \quad a_1 a_2+b_1 b_2+c_1 c_2=0$ $\Rightarrow \quad a+2 b+3 c=0$ Similarly required line perpendicular to $ \frac{x+2}{-3}=\frac{y-1}{2}=\frac{z+1}{5} $ $\Rightarrow \quad-3 a+2 b+5 c=0$ On solving Eqs. (i) and (ii), we get $ \begin{aligned} & \frac{a}{10-6}=\frac{b}{-9-5}=\frac{c}{2+6} \\ & \Rightarrow \quad \frac{a}{2}=\frac{b}{-7}=\frac{c}{4} \\ & \end{aligned} $ $\therefore$ Required line is passing through $(-1,3,-2)$ and having dr's $(2,-7,4)$ $ \therefore \quad \frac{x+1}{2}=\frac{y-3}{-7}=\frac{z+2}{4} $

Asked in: AP EAMCET 2020 (22 Sep Shift 2)

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