3D GEOMETRY DOUBT ;)

IN THIER SOLUTION THEY HAVE MADE THE FIRST PART = 0 AND THEY HAVE OMIITED OUT 'd' AND WHY THEY HAVE DONE SOO
please explain me .. and also show ur approach how to do da sum ;'( [17] [17]

if a plane contains a line.
then,

the point on the line must satisfy the plane eqn. --- (1)

the direction cosines of line X dir cosine of plane =0 ---- (2)

by (1), a² - 3bd - c² =d

by (2), a² - b² - c² =0

from these two,

b²=3bd+d

i have no idea how in the soln.. then have equated the second equation to zero... it has to be 'd'.

sky dats my Q why have they eleiminated d [17]

playpower...

in ur approach..
λ(a²-b²-c²)+(a²+3bd-c²-d²)=0

what u can conclude from here....

For any real λ it is true... so each bracket must be zero...
hence
(a²-b²-c²)=0
and (a²+3bd-c²-d²)=0

woh ans key mein wrong hai shayad se.....