MHTCET 2016 Math Solved Paper

(b) Let direction ratios of a line are (a, b, c).
As, line is perpendicular to the direction ratios (-1 ,2 ,2 ) and (0,2,1).
∴ a × (- 1) + b x 2+ c x 2 = 0 and a x 0 + b x 2 + c x 1 = 0
⇒ - a + 2b + 2c = 0 and 0a + 2b + c = 0
⇒

a

2−4

=

−b

−1−0

=

c

−2−0

⇒

a

−2

=

b

1

=

c

−2

or

a

2

=

b

−1

=

c

2

Hence, direction ratios of a line are (2, -1,2).