bai 1 tim cac stn x y z sao cho x+y+z=xyz

bai 2cmr neu m^2+mn+n^2chia het cho 9 voi m ,n la cac stn thi m,n chia het cho 3

bai 3 tim stn n nho nhat de cac phan so sau toi gian

7/n+9.8/n+10,...,31/n+33

bai 4chung to rang phan so m^3+2m/m^4+3m^2 +1 toi gian

bai 5 a,cmr khong ton tai so chinh phuong nao co dang abab

b,cho 51 so nguyen duong khong vuot qua 100 cmr ton tai 2 so trong 51 so noi tren ma 1 so chia het cho so con lai

c,tim cac so co 3 chu so sao cho hieu cua so ay va gom 3 chu so ay viet theo thu tu nguoc lai la mot so chinh phuong

bai 6cmr A=2x(x+y-1)+y^2+1 luon nhan gia tri khong am voi moi x,y

bai 7 tim hai so nguyen duong sao cho tong ,hieu thuong (so lon chia cho so nho )cua chung cong lai duoc 38

bai 8 cho ba so a,b,c thoa man a/2009=b/2010=c/2011

tinh gia tri cua bieu thuc M=4(a-b)(b-c)-(c-a)^2

bai 1. 11/3.40/13+37/5:7/33-(11/13.1/3+33/7:5/2)

bai 2.tim x

a,3.(x-1)-5.(-7)=(-2)^3-2x

b,2./(1-x)^2+1/-2^2.3=8

bai 3,cho bieu thuc

M=n+1/n+1 - 3-8n/n+1 + 8/n+1

tim cac gia tri cua n de bieu thuc M co gia tri la so nguyen

bai 4,So hoc sinh cua 1 truong ko qua 1000 em,neuxeptoan bo so hoc sinh cua truong do thanh cac hang,moi hang 20 nguoi thi con thieu 5 nguoi,neu xep moi hang 25 nguoi hoac 30 nguoi thi deu thua 15 nguoi , neu xep 42 hang thi vua du . hoi truong do co bao nhieu hoc sinh

bai 5,cho bieu thuc

A=2+2^2+...+2^200

c/m rang

a, A+2 la 1 luy thua cua 2

b, Achia het cho 30

c,A co phai la so chinh phuong ko ? vi sao ?

bai 6,cho 2 bieu thuc

A=1/1+2 + 1/1+2+3 + ...1/1+2+3+...+99

B=1 + 1/2^2+1/3^2 + ...+1/49^2

c/m rang A<B