1234567890 so hang thu tu la so may
viet so tu nhien N =12345678910111213141516...70 ,
a)so N co bn chu so
,b) cs hang don vi cua so 53 dung hang thu may (ke tu trai sang phai moi cs 1 hang),
c) cs viet o hang thu 120 la cs nao?cs do cua so tn nao
a,Tu 1 > 9 co 9 chu so
Tu 10 > 70 co 122 chu so
So N co 9+122=131 chu so
nguoi ta viet lien nhau cac so tu nhien:123456...
a,hoi chu so hang don vi cua so 1998 dung o hang thu may?
b,chu so viet o hang thu 429 la chu so nao?
Nguoi ta viet lien nhau cac so tu nhien : 123456....
a, Hoi chu so hang don vi cua so 1998 dung hang thu may ?
b, chu so viet o hang thu 429 la chu so nao ?
Cho day so:5,21,53,101,165.....
A.So 23765 la so hang thu may cua day ?
B.So hang thu 87cua day la so nao ?
cho day so : 5,21,53,101,165....
A.So 23765 la so hang thu may cua day?
B.So hang thu 87 cua day la so nao?
5=5+8(1^2-1)
...21=5+8(2^2-2)
...53=5+8(3^2-3)
...101=5+8(4^2-4)
...165=5+8(5^2-5)
...a)Ta có (23765-5)/8=n^2-n =>n^2-n-2970=0 =>n=55 (vì n>0)
...b)Số hạng thứ 87 là 5+8(87^2-87)=59861.
cho day 2,11,29,56,92,.. a) tim so hang thu 100 cua day b)so 407 la so hang thu may cua day
cho day 2,11,29,56,92,..
a) tim so hang thu 100 cua day
b)so 407 la so hang thu may cua day
Tong cua 2 so la so tu nhien bang 1092 . Neu o so hang thu nhat lan luot thay chu so hang don vi la 9 thanh 3 ,that chu so hang chuc la 7 thanh 1 thi duoc so hang thu hai .Tim hai so do ? ming cac ban giup minh giai bai toan nay nhe va nho co ca loi giai nha cac ban nhe ?