For positive and

MATHEMATICS · Single correct · ISC · Mathematics · Three-Dimensional Geometry · Three-Dimensional Geometry

Problem

For positive

l, m

and

n

, if the planes

x = ny + mz

y = lz + nx

z = mx + ly

intersect in a straight line, then

l, m

and

n

satisfy the equation (1)

l^2 + m^2 + n^2 = 2

(2)

l^2 + m^2 + n^2 + 2lmn = 1

(3)

l^2 + m^2 + n^2 = 1

(4) None of these