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,


(– )x + (4λ)y + (– 3λ)z = (– 2 – 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


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