数列求和.
求和
1/2*3+1/3*4+...+1/(n+1)(n+2)
参考答案:1/(n+1)(n+2)=1/(n+1)-1/(n+2)
所以
1/2*3+1/3*4+...+1/(n+1)(n+2)
=1/2-1/3+1/3-1/4+1/4-1/5……+1/(n+1)-1/(n+2)[正负相抵消]
=1/2-1/(n+2)
求和
1/2*3+1/3*4+...+1/(n+1)(n+2)
参考答案:1/(n+1)(n+2)=1/(n+1)-1/(n+2)
所以
1/2*3+1/3*4+...+1/(n+1)(n+2)
=1/2-1/3+1/3-1/4+1/4-1/5……+1/(n+1)-1/(n+2)[正负相抵消]
=1/2-1/(n+2)