2/3=1/2+1/6 2/5=1/3+1/15 2/7=1/4+1/28 2/9=1/5+1/45请猜想一般结论,并加以说明.

计算(+5/2)-(-5/3)=-5/1(-5/2)-(-5/3)=5/12/1-3/1=6/1(-2/1)-3/1=-6/1 1+2-3+4-5+6= 5/12-1/6+2/3=? 1+2+3+4+5-6=? -1-6-3+2+5-9=? 1+2+3+4+5+6=? 1+2+3+4+5+6= 1+2+3+4+5+6= 1+2+3+4+5+6= 1+2+3+5+6+1990= 巧算：(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/4+1/5+1/6)-(1+1/2+1/3+1/4+1/5+1/6)*(1/2+1/3+1/4+1/5)(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/4+1/5+1/6)-(1+1/2+1/3+1/4+1/5+1/6)*(1/2+1/3+1/4+1/5)===== 2-(2m+1)/3=(5m-1)/6 3/2x+1-6/5x-1=1 3/2x+1-6/5x-1=1 2x-1/3-1-5x/6=1 5x+1/3-2x-1/6=1 2/3+2/21=?5/6-1/10=? 1+3+5+6-2-1+6=