Bai 1:tim so nguyen P biet P+2va P+4 deu la nguyen to
bai 2: tong 2^100×7×11+81^3 la nguen to hay hop so ( giai thich)
Bai 3: tim so nguyen to P de P +2,p+6,P+8 deu la cac so nguyen to
Cho bieu thuc B= 7/ n -7
a) So nguyen n phai co dieu kien gi de B la phan so.
b) Tim phan so B biet n = -7
c) Tim cac so nguyen n de B la so nguyen.
bn nao co loi giai chi tiet bai nay mk se tick,vi mk dung dien thoai ko viet dau dc nen cac ban thong cam nha.
Bai 1: a)Tim so tu nhien a biet 1960va2002 chia cho a cung co so du la 28
b)Tim 2 sop tu nhien a va b , biet :BCNN(a,b)=300;UCLN(a,b)=15 va a+15=b
Bai 2:a)Tong sau la binh phuong so nao ?
S=1+3+5+7+...+199
b) Cho so ab va so ababab
1)chung to ababab la boi cua ab
2)So 3 va 10101 co phai la uoc cua ababab khong , vi sao?
Bai 3
a)Hay viet them dang sau so 664 ba chu so de nhan duoc sdo co 6 chu so chia het cho 5,9,11
b)Tim so nguyen x thuoc Z biet rang :
(x^2-1)(x^2-4)<0
Bai 4 :tim so nguyen x va y biet: xy-x+2y=3
tim cac stn n sao cho n+1;n+3;n+7;n+9;n+13;n+15 la so nguyen to
Ban nao dung minh se tich
Bai 1Tim nguyen to a de 4a+11 la so nguyen to nho hon 30
Bai 2 cac so sau la so nguyen to hay so hop so:
a=1*3*5*7*....*13+20
b=147*247*347-13
tim tat ca cac so nguyen n sao cho 2n+3/7 la so nguyen
giupppppppppp
Bai 1:tinh hop li
1+2-3-4+5+6-7-8+9+10-...+2006-2007-2008+2009
bai 2:
cho S=31+32+33+...+32014+32015
a)tim so tan cung cua S
B)TIM SO XBIET 3x=2S+3
bai3:
a)cho abc chia het cho 7,chung to rang 2a+3b+c chia het cho 7
b)chung to rang voi moi stn n thi 16n+3 va 12n+2 nguyen t cung nhau
c) tim cac so (x;y) sao cho 34x5y chia het cho ;5;9;2
d) tim stn chia cho 7 du 5;chia 13 du 4
tim so tu nhien n sao cho:n+1; n+3; n+7; n+9; n+11; n+13; n+15 la cac so nguyen to
bai 1 tim so nguyen duong nho nhat co 3 chu so , so nguyen a lon nhat co 2 chu so
bai 2: tim x thuoc Z biet
a, / x/ = -5
b, /x/= <7
c, /x/ = 4
d, /x/=0