1/3+1/5+1/7+.+1/19+1/21=?
1/3*1+1/3*5+1/5*7+----1/17*19+1/19*21=
1/1*3+1/3*5+1/5*7+~1/19*21=简算原理
(1/1+3)+(1/3+5)+(1/5+7)+.(1/19+21)=?(简便计算)
(1+3)/1+(3+5)/1+(5+7)/1+(7+9)/1.+(17+19/1+(19+21)/1=?
1*3/1 + 3*5/1 + 5*7/1+ ……+ 17*19 /1 +19*21/1=
1/3*1+1/3*5+1/5*7+A+1/17*19+1/19*21
计算1/(1×3)+1/(3×5)+1/(5×7)+1/(7×9)+.+1/(19×21)
-1/1*3-1/3*5-1/5*7-1/7*9-^-1/19*21
1+3+5+7+.+21+23+21+19+17+...+7+5+3+1=
1/1×3+1/3×5+1/5×7+…+1/17×19+1/9×21=?
1/1*3+1/3*5+1/5*7+1/7*9.1/17*19+1/19*21结果是多少?
1/1*3+1/3*5+1/5*7+1/7*9.1/17*19+1/19*21怎么做?