问题 选择题 计算:1m+3+6m2-9的结果是( )A.1m-3B.m-3C.1m+3D.m+3 答案 原式=1m+3+6(m+3)(m-3)=m-3(m+3)(m-3)+6(m+3)(m-3)=m-3+6(m+3)(m-3)=m+3(m+3)(m-3)=1m-3.故选A.