∵a³+a²-3a+2=3/a-1/a²-1/a³∴（a³+1/a³）+（a²+1/a²）-3（a+1/a）+2=0（a+1/a）（a²-1+1/a²）+（a+1/a）²-2-3（a+1/a）+2=0（a+1/a）{（a+1/a）²-3}+...