(1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1
来源:学生作业帮 编辑:灵鹊做题网作业帮 分类:数学作业 时间:2024/05/13 11:26:15
(1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)~
方法一
设a=1/2+1/3+1/4;
则原式化简为(1+a)*(a+1/5)-(1+a+1/5)*a
=(a+1/5+a平方+1/5a)-(a+a平方+1/5a)
=1/5
方法二
设1+1/2+1/3+1/4=a,1/2+1/3+1/4=b,则a-b=1.
原式=a×(b+1/5)-(a+1/5)×b
=ab+1/5a-ab-1/5b
=1/5(a-b)
=1/5×1
=1/5
方法三
(1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)
=(1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)+(1/2+1/3+1/4+1/5) -(1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)-(1/2+1/3+1/4)=(1/2+1/3+1/4+1/5)-(1/2+1/3+1/4)=1/5
设a=1/2+1/3+1/4;
则原式化简为(1+a)*(a+1/5)-(1+a+1/5)*a
=(a+1/5+a平方+1/5a)-(a+a平方+1/5a)
=1/5
方法二
设1+1/2+1/3+1/4=a,1/2+1/3+1/4=b,则a-b=1.
原式=a×(b+1/5)-(a+1/5)×b
=ab+1/5a-ab-1/5b
=1/5(a-b)
=1/5×1
=1/5
方法三
(1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)
=(1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)+(1/2+1/3+1/4+1/5) -(1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)-(1/2+1/3+1/4)=(1/2+1/3+1/4+1/5)-(1/2+1/3+1/4)=1/5
一道奥数题,急救!(1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/
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(1+2/1)(1+4/1)(1+6/1).(1+10/)(1-3/1)(1—5/1).(1-9/1)
(1)1+1/2+1/3+1/4+1/5+1/6+1/7+1/14+1/28
(1/2+1/3+1/4+1/5+1/6+.+1/2013)*(1+1/2+..+1/2012)-(1+1/2+1/3+
(1+1/2+1/3+1/4+1/5)*(1/3+1/4+1)-(1+1/3+1/4)*(1/2+1/3+1/4+1/5
(1-1/2)*(1-1/3)*(1-1/4)*(1-1/5)*(1-1/6)*…*(1-1/19)*(1-1/20)=
1/2*1/3+1/3*1/4+1/4*1/5+1/5*1/6 (简便方法)
如何计算:(1-1/2*2)(1-1/3*3)(1-1/4*4)(1-1/5*5)、、、(1-1/2000*2000)拜