The nature of the intersection of the set of planes x + ay + (b + c) z + d= 0, x + by +(c + a)z + d -0 and x+ cy + (a+b)z +d=0?
They meet at a point
They form a triangular prism
They pass through a line
They arc at equal distance from the origin
1 a b+c1 b c+a1 c a+b=1 a a+b+c1 b a+b+c1 c a+b+c=0