Prove each statement. (a) For every integer n, if n2 is an odd, then n is odd. (b) For every integer x, if x2 -2x +7 is even, then x is odd. (c) If x and y are real numbers and x + y is irrational, then x is irrational or y is irrational. (d) If x and y are integers and xy is even, then x is even or y is even. (e) If x and y are integers and x -y is odd, then x is odd or y is odod (f) For every non-zero real number x, if x is irrational, then 1/x is also irrational. (g) If x and y are real numbers and x y> 20, then x > 10 or y > 10. (h) If x and y are positive real numbers and xy> 400, then x> 20 or y > 20 (1) For every real number x, if x is irrational, then -x is also irrational. 0) For every integer n, if n3 is even, then n is even