2B=1+1/2+(1/2)^2+...+(1/2)^98
2B-B=[1+1/2+(1/2)^2+...+(1/2)^98]-[1/2+(1/2)^2+...+(1/2)^99]
B=1-(1/2)^99 <1
3C = 1+1/3+...+(1/3)^98
3C-C=[1+1/3+...+(1/3)^98]-[1/3+(1/3)^2+...+(1/3)^99]
2C=1-(1/3)^99<1=>C<1/2
Chung Minh rang:1+1/2+1/3+1/4+...+1/63 be hon 6
cho A =1/2*3/4*5/6*...*99/100
B=2/3*4/5*6/7*...*100/101
C=1/2*2/3*4/5*...*98/99
a) so sanh A, B, C
b) Chung minh: A*C< A^2< 1/10
c) Chung minh: 1/15< A< 1/10
Lam giup minh di ai lam duoc minh tich dung cho
bai 1 tim so tu nhien nho nhat sao cho khi chia cho 3 du 1 ;4 du 2 ; 5 du 3; 6 du 4 va chia het cho 11
bai 2 chung minh rang 1/22+ 1/32+1/42+......+ 1/1002 be hon 1
bai 3 cho 3n+ 1 la boi cua 10 ( n thuoc Z+)chung minh 3n+4+1 la boi cua 10
giup minh voi !!!!
Cho minh hoi vai bai:
Bài 1: chứng minh
A=1/100+1/101+...+1/200>1/2
B=1/21+1/22+1/23+... Chung minh 5/6<B<4/3
C=1/2^2+1/3^2+...+1/99^2+1/100^2 <3/4
Bai2: tìm x, y
A) x/3-1/y=1/3
B)1/x+y/2=-1/3
C)x/5-2/y=2/15
Chung to rang:1+1/2 mu2+1/3 mu2+1/4 mu2+....+1/100 mu2 be hon 2
cho b= 1/2-1/3+1/4-1/5+.....+1/98-1/99 chung minh 0,2<B<0.4
a)chung minh A= 2^1+2^2+2^3+2^4+...2^2010chia het cho 3
b)chung minh B= 3^1+3^2+3^3+3^4+...3^2010chia het cho 4
c)chung minh C= 5^1+5^2+5^3+5^4+...5^2010chia het cho 6
d)chung minh D= 7^1+7^2+7^3+7^4+...7^2010chia het cho 8
cau 1. Chung minh rang C=2+2^2+2^3+....+2^99+2^100 chia het cho 31
b, Tinh tong C
c,Tim x de 2^2x-1-2=C
CAC BAN GIUP MINH BAIF NAY VOI
Chung minh rang
1 be hon 1/5+1/6+.....+1/16+1/17 be hon 2
