-1/20=-1/4*5, -1/30=-1/5*6, -1/42=-1/6*7, -1/56=-1/7*8, -1/72=-1/8*9, -1/90=9*10
=> -1/4*5+-1/5*6 + -1/6*7 + -1/7*8 + -1/8*9 + -1/9*10=-1/4- -1/5 + ..........= -1/4 - -1/10 = -3/20
-1/20+ -1/30+ -1/42+ -1/56+ -1/72+ -1/90=?
(-1/20)+(-1/30)+(-1/42)+(-1/56)+(-1/72)+(-1/90)
1/20+ 1/30+ 1/42+ 1/56+ 1/72+1/90
1/20+1/30+1/42+1/56+1/72+1/90+... TÍNH.?
A= -1/20 + -1/30 + -1/42 + -1/56 + -1/72 + -1/90 = ?
-1/20+-1/30+-1/42+-1/56+-1/72+-1/90
GIÚP MÌNH NHa
Không quy đồng hãy tính tổng sau: A= -1/20+(-1/30)+(-1/42)+(-1/56)+(-1/56)+(-1/72)+(-1/90)
A=-1/20+-1/30+-1/42+-1/56+-1/72+-1/90+-1/110+-1/132
A = - 1/20 + - 1/30 + - 1/42 + - 1/56 + - 1/72 + - 1/90