1/10+1/15+1/21+...+1/120
=2*(1/20+1/30+1/42+...+1/240)
=2*(1/4*5+1/5*6+...+1/15*16)
=2*(1/4-1/5+1/5-1/6+...+1/15-1/16)
=2*[(1/4-1/16)+(1/5-1.5)+...+(1/15-1/15)]
=2[(4/16-1/16)+0+...+0]]
=2*3/16=3/8
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
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
