1\(7*7-1)+1\(9*9-1)+1\(11*11-1)+••••••1\(99*99-1)求和

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1\(7*7-1)+1\(9*9-1)+1\(11*11-1)+••••••1\(99*99-1)求和

1\(7*7-1)+1\(9*9-1)+1\(11*11-1)+••••••1\(99*99-1)求和
1\(7*7-1)+1\(9*9-1)+1\(11*11-1)+••••••1\(99*99-1)求和

1\(7*7-1)+1\(9*9-1)+1\(11*11-1)+••••••1\(99*99-1)求和
简便计算
1\(7*7-1)+1\(9*9-1)+1\(11*11-1)+••••••1\(99*99-1)
=1/(7-1)(7+1)+1/(9-1)((+1)+1/(11-1)(11+1)+...+1/(99-1)(99+1)
=1/6x8+1/8x10+1/10x12+...+1/98x100
=1/2(1/6-1/8)+1/2(1/8-1/10)+1/2(1/10-1/12)+..+1/2(1/98-1/100)
=1/2(1/6-1/100)
=1/2(50/300-3/300)
=47/600

原式=1/(7-1)(7+1)+1/(9-1)(9+1)+...+1/(99-1)(99+1)
=1/6x8+1/8x10+...+1/98x100
=1/2[1/6-1/8]+1/2[1/8-1/10]+...+1/2[1/98-1/100]
=1/2[1/6-1/100]
=1/2*47/300
=47/600

12-9-7-1 1、7、9题 9+9分之1×9分之7 1/(1/9+1/7)=? 7×9分之1表示 9分之1×7表示 比较大小:(1/5)^(-1/5),(9/7)^(-7/9) 9×7+1 1×9+7有什么特点RT -7,0,1,2,9,（ 7,9,-1,5,( 急 简算:1/1*3+1/3*5+1/5*7+1/7*9+1/9*11 |(1/5)-(1/7)|+|(1/9)-(1/7)|+|(1/9)-(1/11)怎么计算 (1*3)/1+(3*5)/1+(5*7)/1+(7*9)/1+(9*11)/1 1/1*3+1/3*5+1/5*7+1/7*9+1/9*11 (1*3)/1+(3*5)/1+(5*7)/1+(7*9)/1+(9*11)/1 54.2-2/9+4.8-1/7/9 1减9/7除以8/7 (1+1/3+1/5+1/7)*(1/3+1/5+1/7+1/9)-(1+1/3+1/5+1/7+1/9)*(1/3+1/5+1/7) 简算(1+1/3+1/5+1/7)*(1/3+1/5+1/7+1/9)-(1+1/3+1/5+1/7+1/9)*(1/3+1/5+1/7) 简便计算 [1/3-(-1/9+7/12)]*(-36)