Question
If the line 
lies in the plane lx +my -z = 9, then l2 +m2 is equal to
-
26
-
18
-
5
-
2
Solution
D.
2
Since the line
lies in the plane lx my-z =9, therefore we have 2l-m-3 = 0
[∴ normal will be perpendicular to the line]
⇒ 2l-m = 3
and 3l -2m +4 = 9
[∴ point (-3,-2-4) lies on the plane
⇒ 3l-2m = 5
On solving eqs (i) adn (ii), we get
l =1 and m=-1
therefore, l2 +m2 = 2
