1⼀3+1⼀6+1⼀10+1⼀15+1⼀21+1⼀28+1⼀36+1⼀45=？ 怎样用简便方法计算？如果可以请帮写出计算过程，并简要讲解。

1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45
=2(1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90)
=2[1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)+1/(8*9)+1/(9*10)]
=2[(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)+(1/9-1/10)]
=2(1/2-1/10)
=4/5

1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45
=2(1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90)
=2[1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)+1/(8*9)+1/(9*10)]
=2[(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)+(1/9-1/10)]
=2(1/2-1/10)
=1-1/5
=4/5