证明:
易知(n+1)^(-3/2)+(n+2)^(-3/2)+.+(2n)^(-3/2)>0,n>0.
x^(-3/2)是个减函数,(n+1)^(-3/2)最大.则(n+1)^(-3/2)+(n+2)^(-3/2)+.+(2n)^(-3/2)