数学题速求18、19!要过程!
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数学题速求18、19!要过程!
数学题速求18、19!要过程!
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
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)+...+(...
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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
收起
18 = 4.4+（-0.1）+8.333+1.333+（-11.666）
= 4.3 + （-2）
=2.3
19 = [（1-2）+（-3+4）]+[（5-6）+（-7+8）]+。。。[2009-2010]
= [（-1）+1]+[（-1）+1]+。。。。。（-1）
= -1