The value of λ for which the lines $\frac{2-x}{3}=\frac{3-4y}{5}=\frac{z-2}{3}$ and $\frac{x-2}{-3}=\frac{2y-4}{3}=\frac{2-z}{λ}$ are perpendicular is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → $\frac{19}{8}$
A line in the symmetric form,
$\frac{x-x_1}{a}=\frac{y-y_1}{b}=\frac{z-z_1}{c}$
and direction vector: $d(a,b,c)$
First line:
$\frac{2-x}{3}=\frac{3-4y}{5}=\frac{z-2}{3}$
$⇒\frac{x-2}{-3}=\frac{y-\frac{3}{4}}{-\frac{5}{4}}=\frac{z-2}{3}$
$d_1=\left(-3,-\frac{5}{4},3\right)$
Second line:
$\frac{x-2}{-3}=\frac{2y-4}{3}=\frac{2-z}{λ}$
$⇒\frac{x-2}{-3}=\frac{y-2}{\frac{3}{2}}=\frac{z-2}{-λ}$
$d_2=\left(-3,\frac{3}{2},-λ\right)$
$d_1.d_2=0$
$(-3)(-3)+\frac{3}{2}×-\frac{5}{4}-3λ=0$
$⇒3λ=\frac{15}{8}-9=\frac{15-72}{8}$
$⇒λ=\frac{19}{8}$