B = 1 7 + 1 8 + 1 9 + ... + 1 18 + 1 19 < 2 ⇔ 1 7 − 1 7 + 1 8 − 1 7 + 1 9 − 1 7 + ... + 1 18 − 1 7 + 1 19 − 1 7 + 1 20 − 1 7 < 0
Vì 1 8 < 1 7 , 1 9 < 1 7 , ... , 1 20 < 1 7 nên 1 8 − 1 7 < 0 , 1 9 − 1 7 < 0 , 1 10 − 1 7 < 0 , ... , 1 19 − 1 7 < 0 , 1 20 − 1 7 < 0
Vậy B < 0
Chứng tỏ rằng:
1/6+1/7+1/8+1/9+.......+1/18+1/19<2
Chứng minh rằng : 1/5 + 1/6 + 1/7 +...+ 1/16 + 1/17 + 1/18 + 1/19<2
Giúp giải nha
Bài1: chứng minh rằng
1-1/2+1/3-1/4+1/5-1/6+.......-1/1996=1/996+1/997+.....+1/9996
Bài 2:tính
A=1*3*5*7*.....*99/51*52*......*100
Bài 3: Cho A = 1/6*10+1/7*9+1/8*8+1/9*7+1/10*6 chứng minh rằng A= 1/8*(1/6+1/7+1/8+1/9+1/10)
Chứng minh rằng:
A= 1/6+1/7+1/8+...+1/20>1+1/12
B= 1/5+1/6+1/7+...+1/19<1+5/6
a)Tính\(\frac{\left(17\frac{8}{19}-16\frac{9}{18}\right)\left(17,5+16\frac{17}{51}-32\frac{15}{22}\right)}{\frac{7}{3.13}+\frac{7}{13.23}+\frac{7}{23.33}}\)
b) Chứng tò rằng:\(1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{199}-\frac{1}{200}\)\(=\frac{1}{101}+\frac{1}{102}+...+\frac{1}{200}\)
Tính hợp lý:
a) ( -5/6 + 2/5) : 3/8 + ( 4/5 - 11/30) : 3/8
b) (-3/4 + 2/5) : 3/7 + ( 3/5 + -1/4) : 3/7
c)-13/18 . 5/8 + -5/18 . 2/9 + -13/18 . 3/8 + -5/18 . 7/9
d) -11/19 . 4/9 + -8/19 . 3/7 + -11/19 . 5/9 + -9/19 . 4/7
Tính 1) 4/5 +13/18 2) 3/7 -11/8 3) -7/10 - -4/5 4) 3/20 -1/25 5) 2/3 - 5/6 6) 1/4 + -3/8 - 19/10 7) -9/10 - -7/18 8) 3/10 - 11/18 9) 3/5 -5/6 + -7/12 10) -4/9 - (-5 )/6 - 3/8
tính nhanh
a, 2/4+-3/4+15/9+1/9+3/4+7/-10
b, 5/19+-7/15+-19/37+18/-37+14/19+8/15
tìm số nguyên x,biết
-1/8+1/3+(-1)<=x/4,=5/12=-1/6
chiều mik cần gấp òi
chứng tở rằng 1 + 1/2 + 1/3 + 1/4 + 1/5 + 1/6 + 1/7 + 1/8 + 1/9 + 1/10 + 1/11 + 1/12 + 1/13 + 1/14 + 1/15 + 1/16 + 1/17 + 1/18 + 1/ 19 + 1/20 + 1/21 + 1/22 + 1/ 23 + 1/24 + 1/25 + 1/26 + 1/27 + 1/28 + 1/29 + 1/30 + 1/31 + 1/32 < 3
cho a/b = 1/2 + 1/3 + 1/4 + 1/5 + 1/6 + 1/7 + 1/8 + 1/9 với a;b thuộc N. Chứng minh rằng a chia hết cho 11.
