作业帮数学题速求18、19!要过程!
来源：学生作业帮 编辑：作业帮 分类：数学作业 时间：2024/11/01 07:01:13
数学题速求18、19!要过程!
18,
= （4+0.4）+(-0.1)+(8+1/3)-(11+2/3)+(1+1/3)
= (4+8-11+1)+(0.4-0.1)+(-2/3+1/3)
=2+3/10-1/3
=1+(30+9-10)/30
=1+29/30
19,
=(1-2)-(3-4)+(5-6)-(7-8)+(9-10)-(11-12)+...+(2009-2010)
=-1-(-1)+(-1)-(-1)+(-1)-(-1)+...+(-1)
=[-1-(-1)]+[(-1)-(-1)]+[(-1)-(-1)]+...+[(-1)]
=-1
= （4+0.4）+(-0.1)+(8+1/3)-(11+2/3)+(1+1/3)
= (4+8-11+1)+(0.4-0.1)+(-2/3+1/3)
=2+3/10-1/3
=1+(30+9-10)/30
=1+29/30
19,
=(1-2)-(3-4)+(5-6)-(7-8)+(9-10)-(11-12)+...+(2009-2010)
=-1-(-1)+(-1)-(-1)+(-1)-(-1)+...+(-1)
=[-1-(-1)]+[(-1)-(-1)]+[(-1)-(-1)]+...+[(-1)]
=-1