Question

计算：(a-2b)( )=a^2-4ab ; (-m^2-3)( )=9-m^4

Answer 1

9-m^4=（3-m^2）*（3+m^2）=[-(3-m^2)]*[-(3+m^2)]=(-m^2-3)(-3+m^2)

第一个容我再想想.嘿嘿