(1+2+3+4+5+6+7+8+9+10+11+12+13+14+15)x5=?
(1+2+3+4+5+6+7+8+9+10+11+12+13+14+15)x5=?
1x5+2x5+3x5+4x5+5x5… 麻烦给我一个公式.
(7\8-1\5)x5\6=
2x2/1x3+4x4/3x5+6x6/5x7+8x8/7x9+10x10/9x11+12x12/11x13 仔细看看
sn=(2-3x5^-1)+(4-3x5^-2)+…+(2n-3x5^-n)要详解答案,急用!
(9/5X10/7-3/1)X5/6
求前n项和1.1/(2X5),1/(5X8),1/(8X11)...2.2^2/(1X3),4^2/(3X5),6^2/
1十2十3十4十5十6十7十8十9十10x5=几
用简便方法计算!2/7x5/9x(36x28) 7/9÷13/5+2/9x5/13(5/6-7/12x15/14)÷5/
11/4/(2/3-(1/2+3/5)x5/9)怎么算
[(2/3-1/4)÷5/6+4/5]X5/11
2/1x3+2/3X5+2/5x7=2/7x9+2/9x11