Given line is
L:2x+1=5y−1=−1z+1=λ (let)

Let foot of perpendicular is P(2λ−1,5λ+1,−λ−1)
PA=(3−2λ)i^−(5λ+1)j^+(6+λ)k^
Direction ratio of line is
b=2i^+5j^−k^
Now, PA⊥L, so
PA⋅b=0
⇒2(3−2λ)−5(5λ+1)−(6+λ)=0
⇒6−4λ−25λ−5−6−λ=0
⇒−30λ−5=0
⇒λ=−61
So,
P(2λ−1,5λ+1,−λ−1)≡P(α,β,γ)
Now,
α=2(−61)−1=−34⇒α=−34
β=5(−61)+1=61⇒β=61
γ=−λ−1=61−1⇒γ=−65
So,
γβ=−51=−5