Let, 8x+3=2y−4=2z+1=λ.
⇒x=8λ−3,y=2λ+4,z=2λ−1
Let, P≡(8λ−3,2λ+4,2λ−1).
Now, given R(1,2,3) and PR=6&QR=6.
So, by distance formula we get,
⇒(8λ−4)2+(2λ+2)2+(2λ−4)2=36
⇒64λ2+16−64λ+4λ2+4+8λ+4λ2+16−16λ=36
⇒72λ2−72λ=0
⇒λ=0,1
⇒P≡(−3,4,−1)andQ≡(5,6,1)
Hence, centroid of △PQR will be,
(α,β,γ)≡(1,4,1).
⇒α2+β2+γ2=18