Exercise 2. The element 0 is unique. In other words, suppose there are two elements 0 and 0' such that (1) 0+ x = x for all x R and (2) 0' + x = x for all x R. Use (1) and (2) above to show that 0 = 0'. (Hint: this is very short. Since (1) and (2) are true for all x, they are true for any specific choice of x. What values of x will you choose?)