Question

对于任何非零实数a,b定义运算”*”如下,a*b=(a-b)/ab.求2*1＋3*2＋．．．＋10*9的值

Answer 1

a*b=(a-b)/ab=1/b-1/a

2*1＋3*2＋．．．＋10*9

=1/1-1/2+1/2-1/3+1/3-……-1/9+1/9-1/10

=1-1/10

=9/10