a+b=4,b-c=5,则a^2+2b^2+c^2+2ab-2bc

问题描述:

a+b=4,b-c=5,则a^2+2b^2+c^2+2ab-2bc

a^2+2b^2+c^2+2ab-2bc
=(a+b)^2+(b-c)^2
=16+25
=41