1)

a) Complete, including all justifications the following formal demonstration in natural deduction system (Lemmon notation).

(b) Demonstrate , in natural deduction that: x( ), x x.

- N N 1 3. (6(x) (x)) {2, v} 2 (v) A (0) {2,3} 3 () {2,} 4 v (u) {2,v,5} 5 Vx(0(x) + 4(x)) {2, v,5} 6 (v) (v) {2,v,5} 7 4() {2,v,5} 8 1 {2, v} 9 9 Vx(0(x) + 4(x)) 10 Vx(0(2) (x))