1/(1*3)+1/(2*4)+1/(3*5)+1/(4*6)+...+1/(8*10)=?

来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/04 02:19:10
1/(1*3)+1/(2*4)+1/(3*5)+1/(4*6)+...+1/(8*10)=?1/(1*3)+1/(2*4)+1/(3*5)+1/(4*6)+...+1/(8*10)=?1/(1*3)+

1/(1*3)+1/(2*4)+1/(3*5)+1/(4*6)+...+1/(8*10)=?
1/(1*3)+1/(2*4)+1/(3*5)+1/(4*6)+...+1/(8*10)=?

1/(1*3)+1/(2*4)+1/(3*5)+1/(4*6)+...+1/(8*10)=?
29/45

1/(1*3)+1/(2*4)+1/(3*5)+1/(4*6)+...+1/(8*10)
= 1 - 1/3 + 1/2 - 1/4 + 1/3 - 1/5 + 1/4 - 1/6 +...+ 1/8 - 1/10
= 1 + 1/2 - 1/9 - 1/10
= 3/2 - 19/90
= 116/90
= 58/45

1/(1*3)+1/(2*4)+1/(3*5)+1/(4*6)+...+1/(8*10)
=1/2*( 1 - 1/3 + 1/2 - 1/4 + 1/3 - 1/5 + 1/4 - 1/6 +...+ 1/8 - 1/10)
=1/2*(1 + 1/2 - 1/9 - 1/10)
=29/45
楼上的回答忘除2了~

原式=1/(1*3)+1/(3*5)+...+1/(7*9)
+1/(2*4)+1/(4*6)+...+1/(8*10)
=(1-1/3+1/3-1/5+...+1/7-1/9)/2+(1/2-1/4+1/4-1/6+...+1/8-1/10)/2
=(1-1/9)/2+(1/2-1/10)/2
=4/9+1/5
=29/45