@ @YW@ @pý†bɾa@ @ AY B DX C BCXY ABCD AB = BC AD YB x= 1 1 x −1 x2 −x = 1 x2 −x −1 = 0 x = 1± 5 2 ( ) x = 1+ 5 x = AB AD 2 1 120 () 2 . 1000 1000 t s . s − 120 s = 1000 .t = 1000 t s .t + 1 1000 2