(1)结合数轴,∵a<c<0,b>0,
∴a-c<0,b-a>0,c-a>0,
∴|a-c|+|b-a|-|c-a|
=c-a+b-a-(c-a)
=c-a+b-a-c+a
=b-a;
(2)结合数轴,∵a<c<0,b>0,
∴-a+b>0,-c-b>0,-a+c>0
∴|-a+b|-|-c-b|+|-a+c|
=-a+b+c+b+c-a
=-2a+2b+2c;
(3)结合数轴,∵a<c<0,b>0,
∴a+b<0,c-b<0,c-a>0,
∴2c+|a+b|+|c-b|-|c-a|
=2c-a-b-c+b-c+a
=0.