1/9a^2-1/4b^2=(1/2b+1/3a)( )
问题描述：
1/9a^2-1/4b^2=(1/2b+1/3a)( )
(4m+ )^2=16m^2+4m+( )
答
平方差
1/9a^2-1/4b^2=(1/2b+1/3a)(1/3a-1/2b)
(4m+1/2)^2=16m^2+4m+(1/4)