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
Tim so chinh phuong gom 4 chu so biet rang so gom 2 chu so dau lon hon so gom 2 chu so sau 1 don vi.
cho 1 so chinh phuong co 4 chu so. Biet rang chu so tan cung cua no la so nguyen to, tong cac chu so cua no cung la so chinh phuong va can bac 2 cua no co tong cac chu so cung la so chinh phuong
chung minh rang: N=444...44 888...8 9(nchu so 4)( n-1 chu so 8) la so chinh phuong
Tim so tu nhien n co hai chu so biet rang hai so (2n+1) va (3n+1) dong thoi la so chinh phuong.
)Cho A= 111...1555...56 ( n chu so 1 , n-1 chu so 5 ) . Cmr : A la so chinh phuong
Cho a,b,c la cac chu so khac nhau va khac 0.Tim abc biet
a. abc=11.(a+b+c)
b. abc+bca+cab lamot so chinh phuong
c. abc+bca+cab=777
Cho A = 3+3^2 + 3^3+... +3^2016
a, Tinh A
b, Tim chu so tan cung cua A
c,A co la so chinh phuong khong
cho a, b, c, d. chung minh rang a,ad, cd, abcd la so chinh phuong