Tim tong cac so nguyen x . Biet x la so nguyen duong co 2 chu so va x la B ( 5 )

Cau 1: Co tat ca bao nhieu so co 3 chu so ma trong moi so co duy nhat 1 chu so 5.

Cau 2: Biet rang 3n+1 va 5n+4 (n thuoc N) la hai so khong nguyen to cung nhau. Khi do UCLN cua 3n+1 va 5n+4 la bao nhieu.

Cau 3: Tim cap (x;y) nguyen am thoa man:xy+3x+2y+6=0 va lxl+lyl=5.

1) Tim so nguyen to P de co: 

a) P+10 va P+14 deu la so nguyen to

b) P+2 ;P+6 va P+8 deu la so nguyen to

b1 tim so tu nhien lon nhat co 3 chu so biet rang chia cho 5; 7 ; 9 thi co so du lan luot la 2 ; 4 ;6 

b2 tim x biet 

a ) 2x +3 chia het cho x -1

b)3x+5 chia het cho x+1

b3 chung to rang 3n+4 va 4n +5 la 2 so nguyen to cung nhau vs moi so TN

bai 3 cho p la so nguyen to lon hon 3 

A, chung to p co dang 6k+1 hoac 6k+5

B, cho p va 8p-1 la so nguyen to. chung to 8p+1 la hop so

bai 4 

A, tim a va b biet rang a.b=320 va BCNN(a,b)=160

B, tim so tu nhien a nho nhat co 3 chu so sao cho khi chia a cho 11 du 5 va chia cho 13 thi du 8

A = ( x+y)-(z+t)

B = ( x-z)+(y-t)

( A va B la hai so nguyen, so sanh A va B)

a)so sanh E=2018^99-1/2018^100-1 va F=2018^98/2018^99-1

b)Tim so nguyen to ab (a>b>0),biet ab-ba la so chinh phuong

c)Cho abc la so tu nhien co 3 chu so .Tim gia tri lon nhat cua A={abc/a+b+c}+1918

tim so nguyen to p sao cho:

a,p+2 va p+4 la so nguyen to

b,p+2 va p+6 va p+8 la so nguyen to

c,p+10 va p+14 la so nguyen to