Notation: I use
-  \x denotes lambda abstraction

(1) Let M and N be lambda-terms that satisfy the following equations
    M = \ x y. x (M x y)(M x y)
    N = \x y. x (N x x)(N x x)
    Prove that M = N in D_A.


(2) Define P := \x. x y (x x) and M := P P
    Describe the set of approximations of M, A(M)
    NB In the exercises of the previous week, you have drawn the B"ohm
    tree of M.