=2/20+2/10+2/42+..+2/240=2.(1/20+1/30+1/42+...+1/240)
=2.(1/4.5+1/5.6+1/6.7+...+1/15.16)
=2.(1/4-1/5+1/5-1/6+1/6-1/7+...+1/15-1/16)=2.(1/4-1/16)
=3/8 nhé
CHÚC BẠN HỌC GIỎI
K MÌNH NHÉ
1/10+1/15+1/21+...+1/120 = ?
1/10+1/15+1/21+......+1/120 = ?
1/10+1/15+1/21+...+1/120
Tính:B=1/10+1/15+1/21+....+1/120
A= 1/10 + 1/15 + 1/21 + ........+ 1/120
c=1/10+1/15+1/21+...+1/120 = ?
x– 1/10 − 1/15 − 1/21 − ⋯ − 1/120 = 3/8
1 Tính: A=1/10+1/15+1/21/+......+1/120
tính S=1/10+1/15+1/21+1/28+.....+1/120
