因为x＞1,所以｜x-1｜= x-1 ,
｜1-x｜=x-1 ,｜x｜ = x
所以,｜x-1｜+2｜1-x｜+｜x｜
=x-1+2(x-1)+x
=x-1+2x-2+x
=4x-3