The equation of a plane containing the line $x-2=\frac{y-4}{4}=\frac{z-6}{7}$ and parallel to the line…

The equation of a plane containing the line $x-2=\frac{y-4}{4}=\frac{z-6}{7}$ and parallel to the line $\bar{r}=(\hat{i}+3 \hat{\jmath}+5 \hat{k})+\lambda(3 \hat{\imath}+5 \hat{\jmath}+7 \hat{k})$ is
  1. $x-2 y+z=10$
  2. $3 x-2 y+z=4$
  3. $x-2 y+z=9$
  4. $x-2 y+z=0$

Solution

d.r. of given liens are $(1,4,7)$ and $(3,5,7)$. Normal to the plane is perpendicular to them. $\begin{array}{l} =\left|\begin{array}{ccc} \hat{i} & \hat{j} & \hat{k} \\ 1 & 4 & 7 \\ 3 & 5 & 7 \end{array}\right| \\ =\hat{i}(-7)-\hat{j}(-14)+\hat{k}(-7) \\ =-7(\hat{i}-2 \hat{j}+\hat{k}) \end{array}$ Hence eq. of plane is $-7(x-2 y+z)=a$ This plane plasses through point $(2,4,6)$ $\therefore \quad a=-7(2-8+6)=0$ $\therefore$ Eq. of plane is $x-2 y+z=0$

Asked in: MHT CET 2020 (20 Oct Shift 2)

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