Find the equation of the plane through the points (2, 2, – 1) and (3, 4, 2) and parallel to the line whose direction ratios are 7, 0, 6.
We know that the equation of plane passing through (x1,y1,z1) is given by
a(x – x1) + b(y – y1) + c(z – z1) = 0 ……(1)
So, equation of plane passing through (2,2, – 1) is
a(x – 2) + b(y – 2) + c(z + 1) = 0 ……(2)
It also passes through (3,4,2)
So, equation (2) must satisfy the point (3,4,2)
∴ a(3 – 2) + b(4 – 2) + c(2 + 1) = 0
⇒ a + 2b + 3c = 0 ……(3)
We know that line is parallel to plane a2x + b2y + c2z + d2 = 0 if a1a2 + b1b2 + c1c2 = 0 ……(4)
Here, the plane (2) is parallel to line having direction ratios 7,0,6 ,
So,
a×7 + b×0 + c×6 = 0
⇒ 7a + 6c = 0
⇒ ……(5)
Putting the value of a in equation (3)
a + 2b + 3c = 0
⇒ + 2b + 3c = 0
⇒ – 6c + 14b + 21c = 0
⇒ 14b + 15c = 0
⇒
Putting the value of a and b in equation (2)
a(x – 2) + b(y – 2) + c(z + 1) = 0
⇒ (x – 2) +
(y – 2) + c(z + 1) = 0
⇒
Multiplying by we have,
– 12x + 24 – 15y + 30 + 14z + 14 = 0
⇒ – 12x + 15y + 14z + 68 = 0
⇒ 12x – 15y – 14z – 68 = 0
Equation of required plane is 12x – 15y – 14z – 68 = 0