Question

is n=4a solution of the equation 16=3n+4?

Answer 1

Given:
f(n)≡ 16 = 3n +4

Lemma 1:
Determine, if n=4 is a solution of f(n).
16 = 3(4) + 4
16 = 12 + 4
16 = 16 [1]

∵ [1] ∨ f(4) | ∃ n ∈ f(n),
∴ Lemma 1 is true.