1/5x7+1/7x9+1/9x11+1/11x13+…+1/23x25
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1/5x7+1/7x9+1/9x11+1/11x13+…+1/23x251/5x7+1/7x9+1/9x11+1/11x13+…+1/23x251/5x7+1/7x9+1/9x11+1/11x13+…
1/5x7+1/7x9+1/9x11+1/11x13+…+1/23x25
1/5x7+1/7x9+1/9x11+1/11x13+…+1/23x25
1/5x7+1/7x9+1/9x11+1/11x13+…+1/23x25
1/5x7+1/7x9+1/9x11+1/11x13+…+1/23x25
=1/2×（1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13+……+1/23-1/25）
=1/2×（1/5-1/25）
=1/2×4/25
=2/25
1/1x3+1/3x5+1/5x7+1/7x9+1/9x11=?
1/1x3+1/3x5+1/5x7+1/7x9+1/9x11=?
1/5x7+1/7x9+1/9x11+1/11x13+…+1/23x25
1x3分之一+3x5分之一+5x7分之一+7x9分之一+9x11分之一
1/1x3+1/3x5+1/5x7+1/7x9+1/9x11+1/11x13=
1/1x3,1/3x5,1/5x7,1/7x9,1/9x11的通项公式
1 / (5x7) +1 / (7x9) +1 / (9x11)+ 1 / (11x13)+ 1 / (13x15)不能只有答案,
1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11
2/1x3+2/3X5+2/5x7=2/7x9+2/9x11计算..
已知1-1/3=2/1x3,计算1/1x3+1/3x5+1/5x7+1/7x9+1/9x11=
1/(1x3)+1/(3x5)+1/(5x7)+1/(7x9)+1/(9x11).1/(97x99)=多少?这个肯定得用简便方法,请指教.
（1x3）分之1 + （3x5）分之1+ （5x7）分之1 + （7x9）分之1 +（9x11）分之1
1/3十1/3x5十1/5X7十1/7x9十1/9X11十1/11X13
1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11+ +nx(n+1)=
2X/1x3+2X/3x5+2X/5x7+2x/7x9+2x/9x11=10 x=?
有2道分数简便运算奥数题不会.1/2X5+1/3X5+1/8X11+.+1/20X23=?2002/1x3+2002/3X5+2002/5X7+2002/7X9+2002/9X11=?
1/2+1/6+1/12+1/20+1/30+1/42+1/56 ; 1/1x3+1/3x5+1/5x7+1/7x9+1/9x11+1/11x13
(1-1/2x4)x(1-3/3x5)x(1-5/4x6)x(1-7/5x7)x(1-9/6x8)x(1-11/7x9)x(1-13/8x10)x(1-15/9x11)