a-b=3,c-b=3分之1
则a-b-(c-b)=3-3分之1
所以a-c=3分之8
3(a-c)^2+2(c-a)-5
=3(a-c)^2-2(a-c)-5
=[3(a-c)-5][(a-c)+1]
=(8-5)×(3分之8+1)
=11