简便计算,急啊

来源:百度知道 编辑:UC知道 时间:2024/06/09 10:22:11
【1+1/(1*3)】*【1+1/(2*4)】*【1+1/(3*5)】*…………*【1+1/(98*100)】=?

1+1/[n*(n+2)]=(n+1)^2/[n*(n+2)]
原式=[2*2/(1*3)]*[3*3/(2*4)]*[4*4/(3*5)]......*[99*99/(98*100)]
列式后发现,3,4......99都会全部消去,只剩下2/100=1/50

1+1/(2n-1)*(2n+1)=(2n)^2/(2n-1)*(2n+1)(n为整数)
1+1/2n*(2n+2)=(2n+1)^2/2n*(2n+2)(n为正整数)

(1+1/1*3)*(1+1/2*4)*(1+1/3*5)*........*(1+1/98*100)*(1+1/99*101)
=(2/1*2/3)*(3/2*3/4)*....(100/99*100/101)
=(2/1*3/2*4/3...99/98*100/99)*(2/3*3/4*...99/100*100/101)
=(100/1)*(2/101)
=200/101