Let (xn), (yn) be bounded sequences.
a) Prove that lim inf xn + lim inf yn ≤
lim inf(xn + yn) ≤ lim sup(xn +
yn) ≤ lim sup xn + lim sup yn.
Give example where all inequalities are strict.
b)Let (zn) be the sequence defined recursively by
z1 = z2 = 1, zn+2 = √
zn+1 + √ zn, n = 1, 2, . . . . Prove that
(zn) is convergent and find its limit. Hint; argue...