chung minh rang so 2n+1 va 6n+5 nguyen to cung nhau voi moi so tu nhien n
chung minh rang voi moi so tu nhien n, cac so sau la hai so nguyen to cung nhau:
a) 7n + 10 va 5n + 7
b) 2n +3 va 4n +8
chung to rang voi moi so tu nhien N gia tri cua 2 bieu thuc 7n+10 va 5n+7 luon la 2 so nguyen to cung nhau
chung to rang hai so 3n+4 va n+1 la hai so nguyen to cung nhau voi n la so tu nhien khac 0
chung to rang voi moi so tu hien n thi 2n+1 va 2n^2 -1 la hai so nguyen to
Chung to rang voi moi so tu nhien n thi hai so 3n+5 va 5n+8 la hai so nguyen to cung nhau .
Chung to rang:14n+3 va 21n+4 la so nguyen to cung nhau voi n la so tu nhien
a, Cho ( a,b) = 1 . Chung minh rang (a.b, a+b)=1
b, Cho (a,b)= 1. Tim UCLN (11a+2b , 18a +5b)
C,, Cho A = m+n ; B=m^2+n^2.Trong do m va n la cac so tu nhien nguyen to cung nhau. Tim UCLN (A,B)
d, Tim cac so tu nhien n sao cho n^3 - n^2 + n-1la so nguyen to
chung minh rang voi moi so tu nhien n # 0 thi:
a moi so nguyen to lon hon 2 deu co dang 4n _+1
b moi so nguyen t lon hon 3 deu co dang 6n +_1