Chứng minh rằng:
A = 1/3 + 1/32 + 1/33 + ..........+ 1/399 < 1/2
B = 3/12x 22 + 5/22 x 32 + 7/32 x 42 +............+ 19/92 x 102 < 1
C = 1/3 + 2/32 + 3/33 + 4/34 +.........+ 100/3100 ≤ 0
chứng minh
1/22+1/32+1/42+1/52+...+1/1002 >3/4
M = 1002– 992 + 982 – 972 + … + 22 – 12;
N = (202+ 182 + 162 + … + 42 + 22) – (192 + 172 + 152 + … + 32 + 12);
P = (-1)n.(-1)2n+1.(-1)n+1.
\(\frac{1}{30}-\frac{1}{42}-\frac{1}{56}-\frac{1}{72}-...-\frac{1}{2004×2005}\)
1/22 + 1/42 + 1/62 + 1/82 + ... + 1/20222 < 1/2 (gần gấp)
(1/49-1/32).(1/49-1/42).....(1/49-1/492)
Tính:
C= 12*(501x-2004) biết 3*(x-4)= 2003/2004
5^24+5^20+5^16+...+5^4+1/5^26+5^24+5^22+...+5^2+1
Câu hỏi : Cho biết 1 inh sơ = 2,54 cm .Vậy Ti vi loại 42 inh sơ , thì đường chéo màn hình khoảng ?
A.108 cm
B.107 cm
C.115cm
D.106
Tính:
A= 1-4+7-10+.......-2998+3001
B= (1- 1/2)(1- 1/3)(1-1/4).......(1-1/100)
C= (0,8 × 7 + 0,8^2) . (1,25 × 7 × 1,25) + 31,64
D= 9/10×1/90-1/72-1/56-1/42-1/30-1/20-1/12-1/6-1/2
E= 1/2003+1/2004 - 1/2005
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5/2003+5/2004-5/2005
let S be 1!(12+1+1)+2!(22+2+1)+3!(32+3+1)+...+100!(1002+100+1). Find S+1/101!.(as usual, k! = 1.2.3.....(k-1).k)