⇒2a−2b+0c=0 Also, required equation of plane (i) is perpendicular to x+2y+2z=5. ∴a×1+b×2+c×2=0 ∴a×1+b×2+c×2=0 ⇒a+2b+2c=0 Eqs. (ii) and (iii) are identical. ∴
a
−4−0
=
−b
4−0
=
c
4+2
⇒
a
−4
=
b
−4
=
c
6
⇒
a
−2
=
b
−2
=
c
3
=λ (Say) ⇒a=−2λ,b=−2λ,c=3λ On putting the values of a,b and c in Eq. (i), we get