Ta có : (100-99) + (99-98) + .. + (2-1) = 1 + 1 + ... + 1 = 50
(100-99)+(99-98)+...+(2-1)=1+1+...+1(có 50 số hạng)
=1x50
50
tính nhanh (2/3+3/4+5/6+...+99/100).(1/2+2/3+3/4+...+98/99)-(1/2+1/3+...+99/100).(2/3+2/4+...+98/99)
101+100+99+98+...+3+2+1/101-100+99-98+...+3-2+1
Cho A = 100+1/99+2/98+...99/1
B = 100-1/2-2/3-3/4-...-98/99
Tính A/B
A=101+100+99+98+...+3+2+1/101-100+99-98+...+3-2+1
B=3737.43/4343.37
99/1+98/2+97/3+................+2/98+1/99
1/2+1/3+1/4+.......................+1/99+1/100
Tính nhanh
a.(1+1/2)×(1+1/3)×(1+1/4)×...×(1+1/98)×(1+1/99).
b.1/2×2/3×3/4×...×97/98×98/99×99/100
100 + 99/2 + 98/3 + .......... 2/99 + 1/100 : 100/2 + 100/3 +.......+ 100/100+100/101
tính
A=101+100+99+99+98+.........+3+2+1
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101- _100+99-98+.....+3-2+1
1*2*3+2*3*4+3*4*5+....+97*98*99+98*99*100 = ?
