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?

cho ba so a,b,c thoa man 0be honhoac bang a be hon hoac bang b+1 be hon hoac bang c+2 va a+b+c=1 tim gia tri nho nhat cua c

cho a>0,b>0 thoa man a+b lon hon hoac bang 2 .tim max cua M =1/a+b^2 +1/b+a^2

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

cho ba so duong 0 nho hon hoac bang a nho hon hoac hoa bang b nho hon hoac bang c nho hon hoac bang 1 . chung minh a/bc+1+b/ac+1+c/ab+1nho hon hoac bang 2

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)

goi a,b,c la cac canh cua 1 tam giac co 3 duong cao tuong ung la ha,hb,hc. cmr (a+b+c)^2/ha^2+hb^2+hc^2 lon hon hoac bang 4

cho ham so y= f(x) =6/x

tinh f(1) ; f(1.5) ;f(2) ;f(3) ;f(-2/3)

tim x biet y=3 ; y=-2

tim y biet 1<x>3 ; 1.5 be hon hoac bang x lon hon hoac bang 6

diem nao trong cac diem sau day khong thuoc do thi ham s

A(-1;-6 ) ; B(-0.5 ;-12 ) ;C(-0.5 ; -13 ) ; D(-1/3 ; -3 )

Cho cac so duong abcd a+b+c+d =4.cm1/ab+1/cd+1/bc+1/da lon hon hoac bang a2+b2+c2+d2