Question

The direction ratios of the line perpendicular to the lines with direction ratios $1,-2,-2$ and $0,2,1$ are

• A. $2,-1,2$
• B. $-2,1,2$
• C. $2,1,-2$
• D. $-2,-1,-2$

Answer 1

Answer: (A)

$2,-1,2$

Direction ratios of two lines: $<1,-2,-2>$ and $<0,2,1>$

Let direction ratio of required line is $<l,m,n>$

Since, lines are perpendicular,

So, $l-2m-2n=0$ and $2m+n=0$

$\frac{l}{-2+4}=\frac{m}{0-1}=\frac{n}{2-0}$

So, Reuired direction ratio is $<2,-1,2>$

Hence, A is the correct option.