用简便方法计算下面的算式(14+28+39)*(28+39+15)-(14+28+39+15)*(28+3)
问题描述:
用简便方法计算下面的算式(14+28+39)*(28+39+15)-(14+28+39+15)*(28+3)
答
(14+28+39)*(28+39+15)-(14+28+39+15)*(28+3)
=(14+28+39)*(28+39+15)-(14+28+39)*(28+3)-15*(28+3)
==(14+28+39)*(28+39+15-28-3)-15(28+3)
==81×51-15×31
=3666;15(28+3)符号后面-(14+28+39+15)*(28+3)=-(14+28+39)*(28+3)-15(28+3)