Family of Plane's equation can be given by (5+8λ)x+(8−7λ)y+(13+λ)z−(29+20λ)=0 P1 passes through (2,1,3) ⇒(10+16λ)+(8−7λ)+(39+3λ)−(29+20λ)=0 ⇒−8λ+28=0⇒λ=
7
2
d.r, s of normal to P1 ⟨33,
−33
2
,
33
2
⟩ or ⟨1,−
1
2
,
1
2
⟩ P2 passes through (0,1,2) ⇒8−7λ+26+2λ−(29+20λ)=0 ⇒5−25λ=0 ⇒λ=