Question

The direction ratios of a normal to the plane passing through $(0,1,1),(1,1,2)$ and $(-1,2,-2)$ are

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

Answer 1

Answer: (A)

$(1,1,1)$

The $3$ given points are $A(0,0,1),B(0,1,2)$ and $C(1,2,3)$

The dr's of $AB$ are $(0,1,1)$

The dr's of $BC$ are $(1,1,1)$

The normal to the plane will be perpendicular to both these lines.

Hence, $n=AB\times BC$

$n=(0,1,-1)$