[原创]one more D/S

WONDERLAND2004

If x and y are positive integers such that x=8y+12, what is the greatest common divisor of x and y?
1) x=12u, where u is an integer.
2) y=12u, where z is an integer.

OG Page 261 T240, I failed to figure out why the correct answer is B, Anybody can help? Thank you.

lucre

x=8*12*u+12=12(8u+1)    and y=12u

if u and 8u+1 has common divisor a greater than1

u=ab-> 8u+1=8ab+1=a(8b+1/a) hence 1/a is integer, so a=1

WONDERLAND2004

Eventually got it. Thanks a lot.