Find the equation of the plane containing the line and the point (0, 7, –7) and show that the line also lies in the same plane.

we know that equation of plane passing through (x1, y1, z1) is given by

a(x – x1) + b(y – y1) + c(z – z1) = 0 …… (1)


Required plane is passing through (0, 7, – 7) so


a(x – 0) + b(y – 7) + c(z + 7) = 0


ax + b(y – 7) + c(z + 7) = 0 …… (2)


plane (2) also contain line so, it passes through point (– 1, 3, – 2),


a(– 1) + b(3 – 7) + c(– 2 + 7) = 0


– a – 4b + 5c = 0 …… (3)


Also plane (2) will be parallel to line so,


a1a2 + b1b2 + c1c2 = 0


(a)(– 3) + (b)(2) + (c)(1) = 0


– 3a + 2b + c = 0 …… (4)


Solution (3) and (4) by cross – multiplication,





a = – 14, b = – 14, c = – 14


put a, b, c in equation (2),


ax + b(y – 7) + c(z + 7) = 0


(– 14)x + (– 14)(y – 7) + (– 14)(z + 7) = 0


Dividing by (– 14) we get


x + y – 7 + z + 7 = 0


x + y + z = 0


so, equation of plane containing the given point and line is x + y + z = 0


the other line is


so, a1a2 + b1b2 + c1c2 = 0


(1)(1) + (1)(– 3) + (1)(2) = 0


1 – 3 + 2 = 0


0 = 0


LHS = RHS


So, lie on plane x + y + z = 0


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