mc美江 懶人包, mc美江 - 超自然震動, mc美江官方網站, mc美江 燒燬 跳針宣告, mc美江 燒燬 跳針宣告（雲霧加長版）

1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45+1/55=?
Sol
1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110
=1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)+1/(8*9)+1/(9*10)+1/(10*11)
=(3－2)/(2*3)+(4－3)/(3*4)+(5－4)/(4*5)+(6－5)/(5*6)+(7－6)/(6*7)
+(8－7)/(7*8)+(9－8)/(8*9)+(10－9)/(9*10)+(11－10)/(10*11)
=[3/(2*3)－2/(2*3)]+[4/(3*4)－3/(3*4)]+[5/(4*5)－4/(4*5)]+[7/(5*6)－5/(5*6)]
+[8/(7*8)－7/(7*8)]+[9/(9*10)－10/(9*10)]+[11/(10*11)－10/(10*11)
=(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)+(1/10－11/1)
=1/2－1/11
=9/22
So
1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45+1/55=9/11