For each proposition, write a formal proof. (1) Let n be an integer. Then n^2 – n + 4 is even. (2) L

For each proposition, write a formal proof. (1) Let n be an integer. Then n^2 − n + 4 is even. (2) Let n be an integer. If n^3 + n^2 + n + 3 is even, then n isodd. . . .