d(8 - 9/4 + 2/7 ) - (-6 - 3/7 + 5/4 ) - (3 + 2/4 - 9/7 )
=8- 9/4 + 2/7+6+ 3/7 - 5/4 - 3 - 2/4+ 9/7
=(8+6-3) + (- 9/4 - 5/4 - 2/4 ) + ( 2/7 +3/7 + 9/7 )
=11+(-16/4) + 14/7
=11+(-4)+2
=9
e 1/3-3/5+5/7-7/9+9/11-11/13+13/15+11/13-9/11+7/9-5/7+3/5-1/3
=(1/3-1/3)+(3/5-3/5)+(5/7-5/7)+....+13/15
=0+0+0+....+13/15=13/15
f 1/2014-1/2014.2013-1/2013.2012-.....-1/3.2-1/2.1
=1/2014-(1/214.2013-1/2013.2012-....-1/3.2-1/2.1)
=1/2014-(1/2013-1/2014+1/2012-1/2013+...+1/2-1/3+1/1-1/2)
=1/2014-(-1/2014+1)
=1/2014+1/2014-1
=-1006/1007
Chúc bạn học tốt !!