chung minh rang :
S= 1/5+1/13+1/14+1/15+1/61+1/62+1/63<1/2
chung minh rang: 1/5+1/15+1/25+....+1/1985<9/20
cho n la so tu nhien chung minh rang:
a)(n+10)(n+15) chia het cho 2
b)(10n+18n-1):27
chung to rang tong B sau lon hon 1/2 B=1/12+1/13+1/14+1/15+1/16+1/17+1/18+1/19+1/20+1/21+1/22
CMR:1/10^2+1/15^2+...+1/500^2<1/15
bai 1 :
1) x - 10 chia het cho x+3
bai 2 ;chung minh rang
1) S= 2+2^2+2^3+...+2^60 chia het cho 3 , 7 , -15
CMR1/10^2+1/15^2+...+1/500^2<1/15
1. x^10 = 1^x
x^10 = x
(2*x-15)^5 = (2*x-15)^3
2. a co bao nhieu chu so ?
10^20 < a<10^21
3. Cho a = 1+2^2+2^3+..................+2^50
a)Tinh 2a
b)Tinh 2a-a
c)Chung minh a+1 la luy thua cua 2
Cho A=1/2^2+1/3^2+1/4^2+.......+1/20^2 .Chung to rang A<1
Cho A=1/2^2+1/3^2+1/4^2+........+1/20^2 .Chung minh A<1
Chu thich / La phan so
^ la mu
