Engineering
Mathematics
Plane and Its Different Forms
Question

A perpendicular is drawn from a point on the line x − 12 = y + 1−1 = z1 to the plane x + y + z =3 such that the foot of the perpendicular Q also lies on the plane x – y + z = 3. Then the co-ordinates of Q are

(1, 0, 2)

(– 1, 0, 4)

(4, 0, – 1)

(2, 0, 1)

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Solution

Let point P on the line is (2λ + 1, – λ –1, l) foot of perpendicular Q is given by

x−2λ−11=y+λ+11=z−λ1=−(2λ−3)3

∴ Q lies on x + y + z + 3 and x – y + z = 3

⇒   x + z = 3 and y = 0

y=0⇒λ+1=−2λ+33⇒λ=0

⇒ Q is (2, 0, 1)