The equations of a line passing through $(3,-1,2)$ and perpendicular to the lines…

The equations of a line passing through $(3,-1,2)$ and perpendicular to the lines $\overline{\mathrm{r}}=(\hat{\mathrm{i}}+\hat{\mathrm{j}}-\hat{\mathrm{k}})+\lambda(2 \hat{\mathrm{i}}-2 \hat{\mathrm{j}}+\hat{\mathrm{k}})$ and $\bar{r}=(2 \hat{i}+\hat{j}-3 \hat{k})+\mu(\hat{i}-2 \hat{j}+2 \hat{k})$ is
  1. $\frac{x-3}{2}=\frac{y+1}{3}=\frac{z-2}{2}$
  2. $\frac{x-3}{3}=\frac{y+1}{2}=\frac{z-2}{2}$
  3. $\frac{x+3}{2}=\frac{y+1}{3}=\frac{z-2}{2}$
  4. $\frac{x-3}{2}=\frac{y+1}{3}=\frac{z-2}{3}$

Solution

Let $a, b, c$ be the direction ratios of the required line. $\therefore 2 \mathrm{a}-2 \mathrm{~b}+\mathrm{c}=0$ ... (1) and $a-2 b+2 c=0$ From (1) and (2), we write $\begin{aligned} & \frac{\mathrm{a}}{\left|\begin{array}{ll} -2 & 1 \\ -2 & 1 \end{array}\right|}=\frac{\mathrm{b}}{\left|\begin{array}{ll} 2 & 1 \\ 1 & 2 \end{array}\right|}=\frac{\mathrm{c}}{\left|\begin{array}{ll} 2 & -2 \\ 1 & -2 \end{array}\right|} \quad \Rightarrow \frac{\mathrm{a}}{-2}=\frac{\mathrm{b}}{-3}=\frac{\mathrm{c}}{-2} \\ & \therefore(\mathrm{a}, \mathrm{b}, \mathrm{c})=(2,3,2) \end{aligned}$ So equation of required line is $\frac{x-3}{2}=\frac{y+1}{3}=\frac{z-2}{2}$

Asked in: MHT CET 2021 (21 Sep Shift 2)

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