Obtain the equation of the plane passing through the point (1, – 3, – 2) and perpendicular to the planes x + 2y + 2z = 5 and 3x + 3y + 2z = 8.
We know that solution of a plane passing through (x1,y1,z1) is given as –
a(x – x1) + b(y – y1) + c(z – z1) = 0
The required plane passes through (1, – 3, – 2), so the equation of the plane is
a(x – 1) + b(y + 3) + c(z + 2) = 0
⇒ ax + by + cz = a – 3b – 2c …… (1)
Now, the required plane is also perpendicular to the planes,
x + 2y + 2z = 5 and 3x + 3y + 2z = 8
We know that planes a1x + b1y + c1z + d1 = 0 and a2x + b2y + c2z + d2 = 0 are at right angles if,
a1a2 + b1b2 + c1c2 = 0 …… (a)
Using (a) we have,
a + 2b + 2c = 0 …… (b)
3a + 3b + 2c = 0 …… (c)
Solving (b) and (c) we get,
∴a = – 2λ, b = 4λ, c = – 3λ
Putting values of a,b,c in equation (1) we get,
(– 2λ)x + (4λ)y + (– 3λ)z = (– 2)λ – 3(4λ) – 2(– 3λ)
⇒ – 2λx + 4λy – 3λz = – 2λ – 12λ + 6λ
⇒ – 2λx + 4λy – 3λz = – 8λ
Dividing both sides by (– λ) we get
2x – 4y + 3z = 8
So, the equation of the required planes is 2x – 4y + 3z = 8