x1+x2=x2+x3 so x1=x3
以此类推得
x1=x3=x5...=x1999
x2=x4=x6=...=x1998
再可得
1000x1+999x2=1999
x1+x2=1
一不小心又得
x1=1000=x3=x5=...x1999
x2=-999=x4=x6=...x1998
x1+x2=x2+x3 so x1=x3
以此类推得
x1=x3=x5...=x1999
x2=x4=x6=...=x1998
再可得
1000x1+999x2=1999
x1+x2=1
一不小心又得
x1=1000=x3=x5=...x1999
x2=-999=x4=x6=...x1998