级数2/(n+2)(n+1)n 怎么求出答案5
问题描述：
级数2/(n+2)(n+1)n 怎么求出答案
5
答
答
2/[n(n+1)(n+2)] = A/n+B/(n+1)+C/(n+2)= [A(n+1)(n+2)+Bn(n+2)+Cn(n+1)]/[n(n+1)(n+2)]= [(A+B+C)n^2+(3A+2B+C)n+2A]/[n(n+1)(n+2)] ,比较n的同次幂的系数,得A+B+C=03A+2B+C=02A=2联立解得 A=1,B=-2.C=1则 2/[n(n+1...