1/(1x3)+1/(3x5)+1/(5x7)+1/(7x9)+1/(9x11).1/(97x99)=多少?这个肯定得用
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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.
您好
1/(1x3) = (1-1/3)/2
那么1/(1x3)+1/(3x5)+1/(5x7)+1/(7x9)+1/(9x11).1/(97x99)
=(1-1/3)/2+(1/3-1/5)/2+(1/5-1/7)/2+.+(1/97-1/99)/2
=(1-1/3+1/3-1/5+1/5-1/7+.-1/97+1/97-1/99)/2
=(1-1/99)X2
=49/99
1/(1x3) = (1-1/3)/2
那么1/(1x3)+1/(3x5)+1/(5x7)+1/(7x9)+1/(9x11).1/(97x99)
=(1-1/3)/2+(1/3-1/5)/2+(1/5-1/7)/2+.+(1/97-1/99)/2
=(1-1/3+1/3-1/5+1/5-1/7+.-1/97+1/97-1/99)/2
=(1-1/99)X2
=49/99
1/1x3+1/3x5+1/5x7+1/7x9+1/9x11=?
2/1x3+2/3X5+2/5x7=2/7x9+2/9x11
已知1-1/3=2/1x3,计算1/1x3+1/3x5+1/5x7+1/7x9+1/9x11=
2x2/1x3+4x4/3x5+6x6/5x7+8x8/7x9+10x10/9x11+12x12/11x13 仔细看看
因式分解:X15+X14+X13+X12+X11+X10+X9+X8+X7+X6+X5+X4+X3+X2+X+1
计算:1/1x3+1/3x5+1/5x7+1/7x9+……+1/2011x2013
1X3分之一+3X5分之一+5X7分之一+7X9分之一加到2009X2011分之一怎么算,
1+2X3+4X5+6X7+8X9=303
计算:1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+1/6x7+1/7x8+1/8x9+1/9x10.
2/1x3 + 2/3x5 + 2/5x7 +······+ 2/97x99 + 2/99x101 简便计算
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