填空:(2a-b)(a+_)=2a^2-3ab+b^2

问题描述:

填空:(2a-b)(a+_)=2a^2-3ab+b^2

:(2a-b)(a+(-b)=2a^2-3ab+b^2
把后面的式子十字相乘
2a -b
a -b