(1+0.228-0.21)x(0.228-0.21+0.2003)-(1+0.228-0.21+0.2003)x(0.228-0.21)

(1+0.228-0.21)x(0.228-0.21+0.2003)-(1+0.228-0.21+0.2003)x(0.228-0.21)

設0.228-0.21為a,0.228-0.21+0.2003為b.
(1+a)x(b)-(1+b)x(a)
=b+ab-a-ab
=b-a
=0.2003