BITSAT2017MathematicsThree Dimensional GeometryActual
The distances of the point ( 1 , - 5 , 9 ) from the plane x + y + z = 5 measured along a straight line x = y = z is 2 3 k , then the value of k is
Options
- A5
- B6
- C3
- D4
Correct answer
A. 5
Step-by-step solution
Given equation of plane is x + y + z = 5 . The distance measured along the line x = y = z . Direction ratios of the given line is ( 1 , 1 , 1 ) . So, the equation of line P Q is x - 1 1 = y + 5 1 = z - 9 1 = λ ⇒   x = λ + 1 , y = λ - 5 , z = λ + 9 lies on the plane x + y + z = 5 ∴   ( λ + 1 ) - ( - λ + 5 ) + ( λ + 9 ) = 5 ⇒   λ = - 10 The coordinate of Q is ( - 9 , - 15 , - 1 ) and the coordinate of P is ( 1 , - 5 , 9 ) P Q = ( 10 ) 2 + ( 10 )