热心网友
(a-2b-c)^2=[(a-2b)-c]^2=(a-2b)^2-2(a-2b)c+c^2=a^2-4ab+4b^2-2ac+4bc+c^2=a^2+4b^2+c^2-4ab+4bc-2ca.
热心网友
(a-2b-c)^2=(a-2b-c)(a-2b-c)=a^2-2ab-ac-2ab+4b^2+2bc-ac+2bc+c^2=a^2-4ab-2ac+4bc+4b^2+c^2还可进一步简化成：=a(a-4b-2c)+4b(c+b)+c^2
热心网友
(a-2b-c)^2=(a-2b-c)(a-2b-c)=a(a-2b-c)-2b(a-2b-c)-c(a-2b-c)=a^2-2ab-ac-2ab+4b^2+2bc-ac+2bc+c^2=a^2+4b^2+c^2-4ab-2ac+4bc