(1-2)+(3-4)+……+(2013-2014)
由於是两个两个组合,所以一共有2014/2=1007个括号
所以最後答案=-1007
=(1-2)+(3-4)+(5-6)+……+(2011-2012) 每两个一组,分成1006组
=-1-1-1-……-1 每组是-1,共1006个
=-1006
原式=(1-2)+(3-4)+……+(2011-2012)
=-1×(2012÷2)
=-1006
10.25-(6.5+3.5)
=10.25-10
=0.25
1-2+3-4+……+99-100
=(1-2)+(3-4)+……+(99-100)
=(-1)+(-1)+……+(-1)
=(-1)×50
=-50
21.56-0.4*0.4=21.4
21.4-3.84=17.56
3.228×(-9)+3.772×(-9)-(-1.5)×9
=(3.228+3.772+1.5)×(-9)
=8.5×(-9)
=-76.5
1-2-3+4+5-6-7+8+`````+2012
=(1-2-3+4)+(5-6-7+8)+````````
=0
5×1.26+0.24×22+82
≈5×1.3+0.2×20+82
=6.5+4+82
≈7+4+80
=91
≈90
谢谢,清请采纳
3.5+3.5x11+12x6.5
=3.5x(1+11)+12x6.5
=3.5x12+6.5x12
=(3.5+6.5)x12
=10x12
=120