From the de_nition of the backshift operator B, _nd expressions for Bzt and B2zt, if zt is de_ned as: (a) zt = _0, (b) zt = _0 + _1t, (c) zt = _0 + _1xt + _2t, (d) zt = _1xt +_2yt, where _0, _1 and _2...

From the de_nition of the backshift operator B, _nd expressions for Bzt

and B2zt, if zt is de_ned as:

(a) zt = _0,

(b) zt = _0 + _1t,

(c) zt = _0 + _1xt + _2t,

(d) zt = _1xt +_2yt, where _0, _1 and _2 are constants, while xt and yt

are time series.

Hint: The operator B is de_ned by the relationship Bzt = zt􀀀1 for

all t.