= 5(1/1.2+1/2.3+1/3.4+...+1/9.10)
=5(1-1/2+1/2-1/3+1/3-1/4+...+1/9-1/10)
=5(1-1/10)
=5.9/10
=9/2
= 9/2
Nha bẹn :))))
tinh nhanh
\(\frac{5}{2}+\frac{5}{6}+\frac{5}{12}+...+\frac{5}{90}\)= ?
Tính bằng cách thuận tiện nhất:
5/2 + 5/6 + 5/12 + 5/20 + .......... + 5/90
GIÚP MÌNH (
Điền dấu < ; > ; =
3\(\dfrac{1}{5}-\dfrac{8}{3}...........\dfrac{17}{5}-2\dfrac{12}{5}\)
\(\dfrac{1}{31}+\dfrac{1}{32}+\dfrac{1}{33}+....+\dfrac{1}{89}+\dfrac{1}{90}\) ..... \(\dfrac{5}{6}\)
1/2+5/6+11/12+19/20+......+89/90
B=91/2+5/6+11/12+19/20+...+89/90)x100
C=1/2+5/6+11/12+19/20+....+89/90 = ?
Tính nhanh : 1/2 +5/6+11/12+......+89/90+109/110
1/2+5/6+11/12+..+89/90+109/110+10/11
1/2 +5/6 + 11/12 ... + 89/90 + 109/110 + 10/11
