(3a+b)4b-[(2a+b+a-b)b]/2

问题描述:

(3a+b)4b-[(2a+b+a-b)b]/2

原式=(12ab+4b^2)-(3a)b/2
=12ab+4b^2-3ab/2
=(12-3/2)ab+4b^2
=21ab/2+4b^2