1-1/2x1-1/3x1-1/4x1-1/5x1-1/6x1--1/7x1-1/8x1-1/9x1-1/10;

=1-1/2-1/3-1/4-1/5-1/6-1/7-1/8-1/9-1/10;

=1-(6 4 3)/12-(42 35 30)/210 (90 80 72)/720;

=1-13/12-107/210-242/720;

=(50400-54600-25680-16940)/50400;

=-46820/50400;

=-2341/2520