Given that:
A(5,5,2λ), B(1,2,3), C(−2,λ,4) and
D(−1,5,6).
Now,
AB≡(−4,−3,3−2λ)
AC≡(−7,λ−5,4−2λ)
AD≡(−6,0,6−2λ)
Given that A,B,CandD are coplanar.
∴[ABACAD]=0
⇒∣−4−7−6−3λ−503−2λ4−2λ6−2λ∣=0
Expand the determinant along the first row.
⇒−4[(λ−5)(6−2λ)−0]−(−3)[−7(6−2λ)−(−6)(4−2λ)]+(3−2λ)[0−(−6)(λ−5)]
On solving the above equation we get,
∴λ=3,λ=2
We have two values of λ.
⇒λ∈s∑(λ+2)2=(3+2)2+(2+2)2
=41
Hence, λ∈s∑(λ+2)2=41