a-b=2,(1)
a-c=1 (2)
(1)-(2):c-b=1
(2a-b-c)²+(c-b)²
=[(a-b)+(a-c)]²+(c-b)²
=(2+1)²+1²
=10c-b为什么=1a-b=2，(1)a-c=1 (2)(1)-(2):c-b=1