1 原式=1÷7+1/7*99
=1/7+99/7
=(99+1)/7
=100/ 7
2原式=2013×(2011/2012)
=2013×(1-1/2012)
=2013-2013/2012
=2011又2011/2012
如有其它问题请采纳此题后点求助,