cmr : a^2/b^2 +b^2/c^2+c^2/a^2 luon luon lon hon hoac bang c/b+ b/a+ a/c voi a,b,c lon hon 0

CMR so thuc a,b,c thi a^2+b^2+c^2+ab+bc+ca  lon hon hoac bang  0

CMR so thuc a,b,c thi a^2+b^2+c^2+ab+bc+ca  lon hon hoac bang  0

Tïm n thuoc N sao cho

a) 24 : het 2n - 1(n lon hon hoac bang 1)

b) 4n - 7 : het 2n - 1 (n lon hon hoac bang 1)

Khi ta ui cac loai ao quan bang vai soi to tam nen chinh nac nhiet do o :

A Nho hon hoac bang 120C C nho hon 160 do C B Lon hon hoac bang 120 do C D Lon hon 160 do C

Tim x biet:

A. (x-3/4).(3x+1/2)lon hon hoac bang 0 

B. (2x+1).(4x+3)be hon hoac bang 0

1.     cho 4 stn a lon hon hoac bang b, b lon hon hoac bang c, clon hon hoac bang d.

CM:(a-b)(a-c)(a-d)(b-c)(b-d)(c-d)

2.      CM: co the tim dc 1 stn k sao cho: (1997^k)-1 chia het cho 10^4

3.      tong cac chu so cua 1 so chinh phuong co the bang 1995 dc k?

4.      tong cua 1995 stn khac 0 dung bang 1995. Hoi UCLN cua chung la bao nhieu?

hay viet cac tap hop sau bang cach khac 

A={ 9;11;13;...;99] 

B={ 12 ; 24 ; 36 ;48}

M= { THANG 4 ; THANG 6 ;THANG 9 ; THANG 11} 

N =  { X THUOC N / X LON HON HOAC BANG 3 , LON HON HOAC BANG 10} 

Q = { X THUOC N / X LON HON 0 ,BE HON 10}