1.9 The purpose of this exercise is to reinforce your understanding of the use of Leibnig (1.5) along with a hint in proving two expressions equal. For each of the following pair of expressions E[z := X] and E[z := Y], identify a hint X = Y that would show them to be equal and indicate what E is. -EXERCISES FOR CHAPTER 1 23 Be := X] Ez := Y (a) (b) ctytut 'd) ( v + w)yr (e)1.5 Let X , Y, and Z be expressions and z a variable. Let & be an expression, which may or may not contain Z . Here is another version of Leibniz. Leibniz: Z = X, Z -Y Ez : - X| = B|: := Y]