NTA Abhyas JEE Main2020MathematicsThree Dimensional GeometryPractice
If the line x - 4 1 = y - 2 1 = z - m 2 lies in the plane 2 x + l y + z = 7, then the value of m + 2 l is equal to
Options
- A1
- B2
- C- 1
- D- 2
Correct answer
C. - 1
Step-by-step solution
A vector parallel to the line is i ^ + j ^ + 2 k ^ A vector normal to the plane is 2 i ^ + l j ^ + k ^ ∵ the line lies in the plane ⇒ 2 1 + 1 l + 2 1 = 0 ⇒ l = - 4 ∵ Point ( 4,2 , m ) also lies in the plane ⇒ 2 4 + l 2 + m = 7 ⇒   m = 7 Hence, m + 2 l = 7 - 8 = - 1