tim n thuoc N de cac ap so sau nguyen to cung nhau
a) 3n + 2va 7n+1
b) 2n+7 va 5n+2
tim so tu nhien n de 2n+1 va 7n+2 la hai so nguyen to cung nhau
Chung to (2n - 1) va 6n + 5 nguyen to cung nhau voi n thuoc N
chung minh rang 2n+3 va 3n+5 la hai so nguyen to cung nhau (n thuoc N*)
voi n thuoc N chung to 2 so sau nguyen to cung nhau
6n + 5 va 2n + 3
cho A = 1+2+3+4+...+n va B = 2n + 1 ( voi n thuoc N , n lon hon hoac bang 2) chung minh A va B la hai so nguyen to cung nhau
cho a=1+2+3+...+n v b= 2n+1 (voi n thuoc N , n>hoac bang 2 ) . Chung minh rang a va b la 2 so nguyen to cung nhau
Tim stn n sao cho 2n+3 va 4n+1 la 2 so nguyen to cung nhau
tìm số tự nhiên n (n thuộc N ) de : 4n +3 va 2n +3 nguyen to cung nhau